Trejo, Guillermo and Sandra Ley. 2020. Votes, Drugs, and Violence. The Political Logic of Criminal Wars in Mexico. Cambridge University Press.  (2021 Democracy & Autocracy Best Book Award, APSA).

One of the most surprising developments in Mexico’s transition to democracy is the outbreak of criminal wars and large-scale criminal violence. Why did Mexican drug cartels go to war as the country transitioned away from one-party rule? And why have criminal wars proliferated as democracy has consolidated and elections have become more competitive subnationally? In Votes, Drugs, and Violence, Guillermo Trejo and Sandra Ley develop a political theory of criminal violence in weak democracies that elucidates how democratic politics and the fragmentation of power fundamentally shape cartels’ incentives for war and peace. Drawing on in-depth case studies and statistical analysis spanning more than two decades and multiple levels of government, Trejo and Ley show that electoral competition and partisan conflict were key drives of the outbreak of Mexico’s crime wars, the intensification of violence, and the expansion of war and violence to the spheres of local politics and civil society.

Trejo, Guillermo y Sandra Ley. 2022. Votos, Drogas y Violencia. La lógica política de las gueras criminales en México. Penguin Random House. 


Dorff, Cassy, Colin Henry, and Sandra Ley. 2022. “Does Violence Against Journalists Deter Detailed Reporting? Evidence From Mexico.” Journal of Conflict Resolution, 0(0).

Over the last 12 years, Mexico has become one of the most dangerous places to be a journalist. We examine how this risk-environment influences the content and strategies of reporting at one of Mexico’s most well known national newspapers, Reforma. We argue that as the risk environment worsens, journalists use less specific language about armed actors to report on violent events. To test our claims, we turn to three novel sources of data: the first captures granular information about attacks against journalists, the second uses natural language processing to measure changes in reporting overtime; and the third incorporates interviews from journalists themselves. We show that as violence against journalists increases, news story specificity decreases. Importantly, our findings reveal the ways in which journalists develop protection strategies to ensure high quality reporting, even under risky conditions and highlight the critical link between risk and information environments in areas of protracted violence.

Ley, Sandra. 2022. “High-risk participation: Demanding peace and justice amid criminal violence.” Journal of Peace Research, 0(0).

When and why do citizens living amid criminal violence pour into the streets to demand peace and justice, regardless of the risks that protesting in such a context may entail? While victimization experiences provide an initial motivation for participation in protests, this article finds that social networks play a fundamental role for mobilization against insecurity. At an emotional level, socialization within networks helps transform the feelings of individual fear that crime evokes into collective anger that represents potential for action. As individuals become more engaged with one another, their feelings are transformed from being exclusively self-oriented towards other-oriented. Additionally, denser network interactions insulate participants from coercion and generate support mechanisms for their members, creating a sense of security. Thus, networks have the power to transform perceptions of the risks and effectiveness associated with their collective action against crime. Supporting evidence for this argument is derived from original survey data collected in Mexico in 2012. Additionally, in-depth interviews with protest participants reveal the mechanisms through which social networks stimulate protest participation, among both victims and non-victims. This article contributes to the prevailing literature on victimization and political participation and provides new answers on when and how experience with violence can encourage involvement in politics and promote democratic accountability.

Mattiace, Shannan and Sandra Ley. 2022. “Yucatán as an Exception to Rising Criminal Violence in México.” Journal of Politics in Latin America, 14(1), 103-119.

Yucatán state’s homicide level has remained low and steady for decades and criminal violence activity is low, even while crime rates in much of the rest of the country have increased since 2006. In this research note, we examine five main theoretical explanations for Yucatán’s relative containment of violence: criminal competition, protection networks and party alternation, vertical partisan fragmentation, interagency coordination, and social cohesion among the Indigenous population. We find that in Yucatán, interagency coordination is a key explanatory variable, along with cooperation around security between Partido Revolucionario Institucional and Partido Acción Nacional governments and among federal and state authorities.

Altamirano, Melina, Sarah Berens, and Sandra Ley. 2022. “Security or Social Spending? Perceptions of Insecurity, Victimization, and Policy Priorities in Mexico and Brazil.” Political Studies.

In Latin America, deep social inequalities coexist with persistent, high-level criminal violence. Facing competing needs and budget constraints, citizens in the region have to prioritize among different policy choices. We analyze how perceptions of insecurity and crime victimization shape attitudes toward budgetary priorities in social and security policies. Our analysis relies on original data from Mexico and Brazil, two countries exhibiting increased violence at the national level, albeit with important regional variation. We find that exposure to crime takes its toll on citizens’ policy priorities. In both Mexico and Brazil, citizens who feel insecure seem to prioritize public expenditure on the police over social investment policies. Victims of criminal violence are, however, mostly indifferent as to budgetary allocations across the security and social policy fields, suggesting that their spending priorities might diverge from these two spheres of government action or give rise to policy indifference.

Castro, Rodrigo, Ulises Beltrán, Sandra Ley, and René Galicia. 2022. “From election day to presidential approval: Partisanship and the honeymoon period in Mexico.” Electoral Studies, 75, 102438. 

This research analyzes the honeymoon period, the phase between election day and the first quarter of the first year of the presidential term, in which voters form their initial assessment of the new president’s administration, a subject understudied by the literature. While different studies highlight that the president’s approval is strong during the early phase of the administration, we seek to understand why and which are the most important individual-level predictors of early presidential approval. Relying on data from the 2018-19 Mexican Election Study, we argue that voters’ partisanship is key to understanding the attitudes towards the new administration. While co-partisans do not alter significantly their attitudes towards the newly elected President (they already like him), out-partisans are the key group that changed between election day and the honeymoon period: they significantly improved their opinion about the newly elected President. Moreover, as opposed to most studies that identify retrospective evaluations as the most important predictor of presidential approval, this study highlights that, particularly in a honeymoon period—in which election day is still close—expressive postelection attitudes such as satisfaction of democracy or political efficacy are important predictors of early presidential approval, particularly among co-partisans of the newly elected President.

Ley Sandra, J. Eduardo Ibarra-Olivo, Covadonga Meseguer. 2022. “Remittances and Protests against Crime in Mexico.” International Migration Review 56(1): 206-236.

The resource mobilization theory has long emphasized the role of resources in facilitating collective mobilization. In turn, recent research on crime and insecurity in Mexico has drawn attention to the role of local networks of solidarity in facilitating mobilization against crime. We rely on these two literatures to propose that remittances — that is, the resources that emigrants send to their relatives left behind — deserve attention as international determinants of this type of non-violent anti-crime mobilization. Further, relying on recent research on remittances’ impact on political behavior, we hypothesize that the relationship between remittances and contentious action is non-linear, exhibiting a positive effect at low to moderate levels of inflows and declining at higher levels of remittances. We contend that at low to moderate levels, international remittances provide the necessary resources for collective activation. At greater levels of remittance inflows, however, lessened economic and security grievances imply a decline in the probability of protesting. Overall, we show that emigrant remittances matter for organizing protests against criminality at the subnational level but that they produce both an engagement and disengagement effect, depending on the size of the inflows.

Aruguete, Natalia, Ernesto Calvo, Francisco Cantú, Sandra Ley, Carlos Scartascini, and Tiago Ventura. 2021. “Partisan cues and perceived risks: The effect of partisan social media frames during the COVID-19 crisis in Mexico.” Journal of Elections, Public Opinion and Parties, 31:sup1, 82-95.

We present the results of a survey experiment designed to evaluate the effects of social media exposure on perceptions of personal health and job risks during the COVID-19 pandemic in Mexico. Our framing experiment treats respondents to positive and negative partisan messages from high-level politicians. Descriptive findings show divergent evaluations of how the government is addressing the crisis by supporters of the government and opposition parties. Results show that respondents are sensitive to negative frames regardless of the political color of the messenger. Further, supporters of the incumbent are more likely to deflect government’s responsibility when treated with a negative frame by a politician from the opposition.

Ley Sandra, J. Eduardo Ibarra-Olivo, Covadonga Meseguer. 202. “Remittances and Protests against Crime in Mexico.” International Migration Review 56(1): 206-236.

The resource mobilization theory has long emphasized the role of resources in facilitating collective mobilization. In turn, recent research on crime and insecurity in Mexico has drawn attention to the role of local networks of solidarity in facilitating mobilization against crime. We rely on these two literatures to propose that remittances — that is, the resources that emigrants send to their relatives left behind — deserve attention as international determinants of this type of non-violent anti-crime mobilization. Further, relying on recent research on remittances’ impact on political behavior, we hypothesize that the relationship between remittances and contentious action is non-linear, exhibiting a positive effect at low to moderate levels of inflows and declining at higher levels of remittances. We contend that at low to moderate levels, international remittances provide the necessary resources for collective activation. At greater levels of remittance inflows, however, lessened economic and security grievances imply a decline in the probability of protesting. Overall, we show that emigrant remittances matter for organizing protests against criminality at the subnational level but that they produce both an engagement and disengagement effect, depending on the size of the inflows.

Ley, Sandra, J. Eduardo Ibarra-Olivo, and Covadonga Meseguer. 2021. “Family Remittances and Vigilantism in Mexico.” Journal of Ethnic and Migration Studies 47(6): 1375-1394. DOI:

We explore the role of workers’ remittances in supporting vigilante organisations that emerged in reaction to rising criminal violence in Mexico. Research on remittances posits both a positive and a negative effect on collective action from the reception of remittances. On one hand, remittances sent by relatives abroad provide extra resources for political action at home. On the other hand, the reception of remittances makes recipients less prone to protesting, through a reduction in grievances. As a result, remittances can be associated with both an increase and a decrease of collective political activity. In this paper, we claim that both effects can co-exist and that the predominance of one mechanism or the other depends on the degree of penetration of remittances at the municipal level. Using data on the existence of vigilante organisations, we find that in most remittance-receiving municipalities, through a resource effect, remittance inflows increase the probability of observing self-defense organisations, but this probability declines at high rates of remittance penetration at the local level. Nonetheless, we observe an activation effect in a majority of remittance receiving municipalities. The paper contributes both to our understanding of international social networks as determinants of civilian action and to the research agenda on how workers’ remittances shape political behaviour in home countries.

Trejo, Guillermo and Sandra Ley.  2021. “High-Profile Criminal Violence: Why Drug Cartels Murder Government Officials and Party Candidates in Mexico.” British Journal of Political Science 51(1): 203-229. (Honorable Mention at APSA 2020 Democracy and Autocracy Section).

This article explains a surprising wave of lethal attacks by drug cartels against hundreds of local elected officials and party candidates in Mexico, 2007-2012. These attacks are puzzling because criminal organizations prefer the secrecy of bribery over the publicity of political murder. Scholars suggest that war drives armed actors to attack state authorities in search of protection or rents. Using original data of high-profile attacks in Mexico, we show that war need arguments underexplain violence. Focusing on political opportunities, we suggest that cartels use attacks to establish criminal governance regimes and conquer local governments, populations, and territories. We present quantitative and qualitative evidence showing that cartels took advantage of Mexico’s political polarization and targeted subnational authorities who were unprotected by their federal partisan rivals. Cartels intensified attacks during subnational election cycles to capture incoming governments and targeted geographically adjacent municipalities to establish controls over large territories. Our findings reveal how cartels take cues from the political environment to develop their own de facto political domains through high-profile violence. These results question the widely shared assumption that organized criminal groups are apolitical actors.

Altamirano, Melina and Sandra Ley. 2020. “The Economy, Security, and Corruption in the 2018 Presidential Election. Campaign issues and electoral preferences in Mexico.” Política y gobierno, 27(2). Special bilingual volume on the 2018 Mexican Election. Español English

Throughout Enrique Peña Nieto’s administration and during the 2018 presidential campaign, three problems stood out among the Mexican electorate: the limited economic growth, a sustained increase in violence, and multiple corruption scandals. Therefore, based on the National Electoral Survey of Mexico (ENEM) 2018, we analyze the simultaneous effects of individual evaluations of the economy, violence and corruption on electoral preferences. Our findings indicate the prevalence of a retrospective economic vote that coexists with a security vote, but without clear support from crime victims. Although corruption was widely discussed during the electoral campaign, this issue did not play a major role in voter preferences.

Castro Cornejo, Rodrigo, Sandra Ley and Ulises Beltran. 2020. “Anger, Partisanship, and the Activation of Populist Attitudes in Mexico.” Política y gobierno, 27(2). Special bilingual volume on the 2018 Mexican Election. EspañolEnglish

This article analyzes the populist activation of the electorate during the 2018 presidential election in Mexico, which requires a set of conditions. First, voters need to report grievances about the country’s political, economic, and social situation. Moreover, it is necessary the role of ambi-tious politicians to make those grievances salient among voters, in order for voters to be responsive to candidate’s populist rhetoric and translate their anger into electoral behavior. However, as opposed to previous studies, we argue that not every voter will be mobilized as a response to populist rhetoric, even if they register the same level of populist attitudes. Consistent with the political behavior literature, we argue that voters’ party identification constitutes a filter of information that makes co-partisan voters more likely to accept the populist rhetoric when it is consistent with their political predispositions. In other words, if the populist rhetoric contradicts voters’ partisanship, voters will reject the candidate’s populist rhetoric even though those voters report a high level of populist attitudes.

Altamirano, Melina, Sarah Berens, and Sandra Ley. 2020. “The Welfare State amid Crime: How Victimization and Perceptions of Insecurity Affect Social Policy Preferences in Latin America and the Caribbean.” Politics and Society, Special issue on “Societies under Stress.” (2021 Seligson Prize from LAPOP)

Criminal violence is one of the most pressing problems in Latin America and the Caribbean, with profound political consequences. Its effects on social policy preferences, however, remain largely unexplored. This article argues that to understand such effects it is crucial to analyze victimization experiences and perceptions of insecurity as separate phenomena with distinct attitudinal consequences. Heightened perceptions of insecurity are associated with a reduced demand for public welfare provision, as such perceptions reflect a sense of the state’s failure to provide public security. At the same time, acknowledging the mounting costs and needs that direct experience with crime entails, victimization is expected to increase support for social policies, particularly for health services. Survey data from twenty-four Latin American and Caribbean countries for the period 2008–12 show that perceptions of insecurity indeed reduce support for the state’s role in welfare provision, whereas crime victimization strongly increases such preferences.

Ley, Sandra and Magdalena Guzmán. 2019. “Doing Business amid Criminal Violence. Companies and Civil Action in Mexico.” In D. Avant, M. Berrie, E. Chenoweth, R. Epstein, C. Hendrix, O. Kaplan, and T. Sisk. Civil Action and the Dynamics of Violence. Oxford: Oxford University Press, pp. 147-177.

Criminal violence has risen dramatically across Mexico in the last decade, and it has had devastating economic, social, and political consequences. How have Mexicans reacted to these violent trends? This chapter explores the civil actions of the Mexican business sector and their potential effects. It focuses on Monterrey, Mexico, where companies actively helped to create a new, more accountable police force, launched an innovative crime-reporting mechanism to better monitor and prosecute crimes, and engaged with local governments to enhance political accountability and citizen oversight. The chapter briefly compares the experience of the business sector in Monterrey with that of Ciudad Juárez and Acapulco, where the role of businesses respectively resulted in an array of broader civil and “uncivil” actions amid criminal violence,. Overall, the chapter shows that in the face of organized crime, the private sector and governments can potentially collaborate with each other, both as allies and as a system of societal checks and accountability.

Ley, Sandra, Shannan Mattiace, and Guillermo Trejo. 2019. “Indigenous Resistance to Criminal Governance. Why Regional Ethnic Autonomy Institutions Protect Communities from Narco Rule in Mexico.” Latin American Research Review 54(1): 181-200.

This article explains why some indigenous communities in Mexico have been able to resist drug cartels’ attempts to take over their local governments, populations, and territories while others have not. We argue that while indigenous customary laws and traditions provide communal accountability mechanisms that make it harder for narcos to take control, they are insufficient. Using a paired comparison of two indigenous regions in the highlands of Guerrero and Chihuahua – both ideal zones for drug cultivation and traffic–we show that communities most able to resist narco conquest are those that have a history of social mobilization, expanding village-level indigenous customary traditions into regional ethnic autonomy regimes. By scaling-up local accountability practices regionally and developing trans-local networks of cooperation, indigenous movements have been able to construct mechanisms of internal control and external protection that enable communities to deter the narcos from corrupting local authorities, recruiting young men, and establishing criminal governance regimes imposing rule through force.

Ley, Sandra. 2018. To Vote or Not to Vote: How Criminal Violence Shapes Electoral Participation. Journal of Conflict Resolution 62(9): 1963-1990

Organized crime-related violence has important electoral consequences. Analyses of aggregate panel data on Mexican elections and an original post-electoral survey conducted in Mexico show that the strategic use of violence by organized crime groups during electoral campaigns demobilizes voters at large. Regions where criminal organizations attempted to influence elections and politics by targeting government officials and party candidates exhibited significantly lower levels of electoral participation. Consistently, at the individual level, results reveal that voters living in regions where organized crime engaged in high-profile violence were more cautious when deciding whether to vote or not. Prior research has focused on the role of crime victimization in non-electoral participation, but the empirical evidence presented here suggests that the impact of a criminal context on turnout transcends personal victimization experiences.

Trejo, Guillermo and Sandra Ley. 2018. “Why Did Drug Cartels Go to War in Mexico? Subnational Party Alternation, the Breakdown of Criminal Protection, and the Onset of Large-Scale Violence.” Comparative Political Studies 51(7): 900-937 (Award for Best Paper Published in CPS in 2018)

This article explains why Mexican drug cartels went to war in the 1990s, when the federal government was not pursuing a major anti-drug campaign. We argue that political alternation and the rotation of parties in state gubernatorial power undermined the informal networks of protection that had facilitated the cartels’ operations under one-party rule. Without protection, cartels created their own private militias to defend themselves from rival groups and from incoming opposition authorities. After securing their turf, they used these militias to conquer rival territory. Drawing on an original database of inter-cartel murders, 1995–2006, we show that the spread of opposition gubernatorial victories was strongly associated with inter-cartel violence. Based on in-depth interviews with opposition governors, we show that by simply removing top- and mid-level officials from the state attorney’s office and the judicial police – the institutions where protection was forged – incoming governors unwittingly triggered the outbreak of inter-cartel wars.

Aldrich, John, Gregory Schober, Sandra Ley, and Marco Fernández. 2018. “Incognizance and Perceptual Deviation: Individual and Institutional Sources of Variation in Citizens’ Perceptions of Party Placements on the Left–Right Scale.” Political Behavior 40 (2): 415-433.

In this paper we use comparative study of electoral systems data to understand the variation in citizens’ perceptions of political party placements on the left–right scale. We estimate multilevel models to assess the extent to which individual characteristics, party characteristics, and institutional designs contribute to variability observed in citizens’ perceptions of party placements. Because lack of information on the part of the citizens may be revealed through failure to respond to the left–right scale questions or through random components to actual placements, we develop models that include assessments of both types of responses to reduce bias from considering only one source. We find that individual-, party-, and institutional-level variables are relevant to understanding variation in citizens’ perceptions of party placements. Finally, we demonstrate that an inability to cognize the left–right scale (incognizance) and a deviation in the perceptions of party positions (perceptual deviation) have important consequences for citizens’ thermometer evaluations of political parties.

Cantú, Francisco and Sandra Ley. 2017. “At the Polling Station: The Determinants of Citizen Participation in the Organization of Elections.” Election Law Journal 16(4): 495-510.

Citizen participation is crucial for the strengthening of democracy. However, the literature has largely focused on voter turnout, dismissing an equally important role that citizens play on Election Day: their role as poll workers. Moreover, our knowledge of the determinants of political participation is limited, as most of the existing evidence comes from survey data. To address these substantive and methodological gaps, we take advantage of an original feature of the Mexican election system: the participation of randomly selected citizens to organize and oversee the operation of polling stations. We argue that the socio-political context in which elections take place greatly affect citizen participation in them. In particular, for the study of nascent democracies, studies of political participation must incorporate two dynamic processes that many of them face: the contested legitimacy of electoral institutions and rising violence. The nature of our dataset allows us to address the measurement problems frequently associated with empirical analyses that use self-reported participation, which weakens the validity of their conclusions.

Meseguer, Covadonga, Sandra Ley, and J. Eduardo Ibarra-Olivo. 2017. “Sending Money Home in Times of Crime: The Case of Mexico.” Journal of Ethnic and Migration Studies, 43(13): 2169-2192.  

We explore at the municipality level how the climate of criminal violence has affected the flow of remittances to Mexico. Using a panel of municipalities in the years 2006 and 2010, we find that drug-related crimes and overall rates of homicides have reduced the percentage of families that receive remittances. This result is robust to controlling for net migration, political variables, and traditional socioeconomic explanations of remittance sending. It is also robust to potential threats to validity. We interpret this result as suggestive of self-interested concerns when sending money home amidst a climate of rampant violence. Nonetheless, mixed motivations to remit are evident in our analysis.

Ley, Sandra. 2017. “Security and Crime Issue Voting: Electoral Accountability in the Midst of Violence.” Latin American Politics and Society 59(1): 3-27.

Rising levels of crime and insecurity affect quality of life. A fundamental question for the prospects of democracy is whether voters, in hopes of reaching better solutions to conditions of prevailing insecurity, can hold their elected officials accountable for such situations. This article argues that electoral accountability amid criminal violence requires voters to be able to assign responsibility for crime and that partisan alignment across levels of government facilitates this task. Recent Mexican elections are examined in order to test this argument. Relying on both aggregate electoral data and individual survey evidence, this paper shows that voters hold politicians accountable for crime in the narrow circumstances of organized crime-related violence and political alignment. This evidence not only provides additional caveats to issue voting models, but also opens new avenues of research on electoral accountability.

Trejo, Guillermo and Sandra Ley. 2016. “Federalism, Drugs, and Violence. Why Intergovernmental Partisan Conflict Stimulated Inter-cartel Violence in Mexico.” Política y Gobierno 23(1): 9-52. Special bilingual volume on Democracy, Conflict, and Violence in Latin America

The dominant view of the dramatic increase of criminal violence in Mexico following the 2007 federal intervention in the War on Drugs suggests that inter-cartel violence became particularly intense in subnational regions where the president could not coordinate the federal government’s actions with subnational opposition rulers but came under control where the president worked with his co-partisans. In this article we challenge the “coordination” argument and claim that in contexts of acute political polarization between Left and Right – like the one Mexico experienced before the War on Drugs – partisan conflict can motivate federal authorities to develop cooperative military and policing interventions in regions where the president’s co-partisans rule, but to deliberately neglect effective assistance to the president’s main political rivals and then blame the violence on them. Based on an original dataset of inter-cartel violence in Mexico (2006-2012), we show that while criminal violence was more intense in municipalities from states ruled by opposition parties, it was five times greater in cities ruled by the Left – the president’s political nemesis. We use case studies to show how Mexico’s conservative federal government followed differentiated strategies to deal with spirals of drug violence: it worked together and protected subnational co-partisans (PAN); partially cooperated with centrist opposition authorities (PRI); but confronted leftist governors and mayors (PRD) and left them at the mercy of drug cartels. Our results are consistent with findings in conflict studies showing that state agents do not always seek the monopoly on violence and sometimes tolerate violence to punish their political enemies.