Political Science Voter Turnout Field Experiments
Christopher Larimer
  • LAST REVIEWED: 02 April 2020
  • LAST MODIFIED: 24 May 2018
  • DOI: 10.1093/obo/9780199756223-0243


Voter mobilization field experiments, often referred to as “get out the vote,” or GOTV field experiments, are targeted efforts—mostly by scholars but occasionally in coordination with campaigns—to apply experimental methods to the study of voter turnout. These studies are conducted in the “real world,” meaning voters are randomly assigned to receive a treatment, or no treatment. These treatments, often in the form of mail, door knocking, phone calls, text messages, and more recently social media, encourage voters to vote in an upcoming (usually within one to two weeks) election. Importantly, voters are unaware of their participation in the experiment. Following the election, scholars observe whether the treatments resulted in different turnout rates across the experimental groups. As Donald Green and Alan Geber note in the third edition of their seminal book, Get Out the Vote, in the 2000s and 2010s, these types of experiments have seen increased attention as campaigns have become more data driven and their methods for targeting voters more sophisticated. Green and Gerber trace the first attempt at a voter mobilization field experiment to a study by Harold Gosnell in Chicago prior to the 1924 presidential election. Only a few other studies were conducted over the next several decades until the publication of Gerber and Green’s foundational article in 2000. Since that time, hundreds of articles have appeared in political science journals documenting results from voter mobilization field experiments. These studies, primarily conducted in the United States, have generally focused on testing whether certain types of messages (usually nonpartisan, and randomly assigned to voters) increase the likelihood of voting. While the sophistication with which these experiments are administered has increased, the basic design has remained static: voters are randomly assigned to experimental groups, a treatment is administered, and then an outcome variable is measured to assess whether the treatments significantly affected individual behavior: most often, the act of voting. In their book, Field Experiments, Gerber and Green lay out in great detail the appropriate methodological steps and techniques for conducting GOTV field experiments, as well as their advantages over other research designs. Unlike traditional survey research based on correlational analysis, because voters are randomly assigned to treatment and control groups, field experiments allow for testing of causal effects. Furthermore, field experimental studies that rely on official voting records are able to avoid the mistakes and biases associated with self-reported attitudes and behavior common in survey research. Voter mobilization field experimental research has generated considerable practical value to campaigns but also presented some challenges as scholars and practitioners disagree on the extent to which real-world campaigns should be used to test theories of political behavior, including randomly assigning voters to receive contact, or no contact, from a real campaign.

General Overviews

The formative and most influential work on voter mobilization field experiments is Green and Gerber 2015. The book is now in its third edition, with each revision updating its set of recommendations as to what campaign tactics are most effective for mobilizing voters. Summarizing the entirety of their research, Gerber and Green write, “the more personal the interaction between campaign and potential voter, the more it raises a person’s chances of voting” (p. 9). Gerber and Green 2017 provides an updated and condensed version of this literature focused more on summarizing findings across field experiments for the purposes of studying political behavior from an academic perspective. This chapter is more quantitative than Green and Gerber 2015 and provides a meta-analysis of all direct mail voter mobilization studies to date. Green, et al. 2013 similarly reviews voter mobilization field experiments, providing average treatment effects across studies by message type and mode of delivery. The general conclusion of both meta-analyses is that “interpersonal” messages, or those invoking some form of social pressure language, are significantly more effective at increasing turnout than those that do not contain such elements. Since this encyclopedia entry cannot cover all voter mobilization field experiments (which number in the hundreds) Gerber and Green 2017 and Green and Gerber 2015 are valuable resources with exhaustive lists of published and unpublished studies, while Green and Gerber 2005 presents data from twelve different studies. Reviewing the more significant voter mobilization field experiments, Gerber and Green 2017 concludes that phone calls generally have the weakest effect on turnout, subject to the message and “quality” of the call, while canvassing tends to consistently produce the largest treatment effects on voter turnout.

  • Gerber, Alan S., and Donald P. Green. “Field Experiments on Voter Mobilization: An Overview of a Burgeoning Literature.” In Handbook of Economic Field Experiments. Vol. 1. Edited by Abhijit Vinayak Banerjee and Esther Duflo, 395–438. Amsterdam: Elsevier, 2017.

    DOI: 10.1016/bs.hefe.2016.09.002

    Short of a book-length study, this is far and away the most comprehensive overview of the entire field. Methodological advantages of field experiments over survey or observational research are thoroughly discussed. The chapter also provides a list of all direct-mail voter mobilization field experiments from 1998–2014 with treatment effects and message type. The meta-analysis at the end of the chapter is a valuable resource for scholars working in this area.

  • Green, Donald P., and Alan S. Gerber, eds. Special Issue: The Science of Voter Mobilization. The ANNALS of the American Academy of Political and Social Science 601 (2005).

    Entire issue of this journal is devoted to voter mobilization field experiments. Green and Gerber provide an overview of recent (at the time) findings, followed by a dozen essays reviewing original or existing field experimental data on voter turnout. Importantly, these essays note the heterogeneity in treatment effects across subpopulations.

  • Green, Donald P., and Alan S. Gerber. Get Out the Vote: How to Increase Voter Turnout. 3d ed. Washington, DC: Brookings Institution, 2015.

    Seminal work on voter mobilization field experiments. This book summarizes results from hundreds of experiments in order to document what works (and what does not) in terms of mobilizing voters. This is considered by many to be an essential resource for campaign operatives as well as scholars. Each chapter includes a summary of findings, labeled as “lessons learned,” relevant to campaigns.

  • Green, Donald P., Mary C. McGrath, and Peter M. Aronow. “Field Experiments and the Study of Voter Turnout.” Journal of Elections, Public Opinion & Parties 23.1 (2013): 27–48.

    DOI: 10.1080/17457289.2012.728223

    Reviews extant literature on voter mobilization field experiments, summarizing average treatment effects for field experiments using direct mail, robo calls, canvassing, and text messages. Results indicate treatment effects on voter turnout for all modes of contact (phone calls, text, mail, canvassing) increase when utilizing some form of “personal” messaging.

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