Do Robotic Calls from Credible Sources Influence Voter Turnout or Vote Choice?

James G. Gimpel
Daron R. Shaw
Fieldwork by:
Texas, United States of America
463,529 Republican Voters
2006 - 2006
Target group:
  • Voters
Outcome of interest:
  • Electoral participation
  • Voter Behavior
Intervention type:
  • Nudges and reminders
AEA RCT registration number:

Automated phone calls remain an important communication channel for political campaigns, touted as a low-cost means of reaching targeted voters, even though evidence is mixed on their effectiveness. To test the impact of an automated phone call from a credible source on voters’ preferences and behavior, researchers delivered the message to random voters in two concurrent randomized evaluations. The call did not increase voter turnout or change voter preferences, suggesting that automated phone calls may not be a cost-effective strategy for communicating with and mobilizing constituents.

Policy issue

Although restricted by law in approximately half of U.S. states, automated phone calls remain an important communication channel for many political campaigns, as a low-cost means of reaching large numbers of targeted voters. If inexpensive, automated phone calls affect voters even modestly, they might represent an attractive option for campaigns—especially late in the race, when money is tight and candidates fight to hold voters’ attention. But voters’ indifference to impersonal forms of communication may lead them to ignore or discount the message, undermining automated calls’ effectiveness in increasing turnout. Can a persuasive message delivered by a particularly credible source impact not only voter mobilization but also voters’ candidate choices?

Context of the evaluation

This evaluation coincided with the closing days of the March 2006 Texas Republican Primary election. Races on the ballot included all statewide executive offices, including governor, and two statewide judicial elections. In the contest of interest for this evaluation, incumbent Justice Don Willett faced a challenge from Steve Smith for a position on the Texas Supreme Court.

Willett had been appointed to fill a vacancy on the bench the previous August by Governor Rick Perry. In an effort to combat what was thought to be a serious threat from the opposing candidate, Governor Perry recorded an automated phone call on Willett’s behalf to be delivered the day before the primary. Willet’s campaign directed the call at more than 200,000 households that were both likely primary voters and strong Perry supporters.

Details of the intervention

In collaboration with Don Willet’s campaign, researchers evaluated the effect of the campaign’s automated calls on both voter turnout and vote choice, through two concurrent evaluations that randomized the delivery of the call program in two different ways.

For the first evaluation, to examine the calls’ impact on voter turnout and vote choice, researchers delivered the call to all Republican households in a randomly chosen half of 1,597 precincts containing between 100 and 700 identified Republican and pro-Perry households. Households in comparison precincts did not receive the call.

The second evaluation explored the automated call’s effect on voter mobilization only within precincts containing fewer than 100 or more than 700 Republican households. Among all 170,927 Republican households in these precincts, researchers randomly assigned half to receive the call, while the other comparison households did not, and formed the comparison group.

The automated call’s source and content were designed to maximize effectiveness. Governor Perry—who enjoyed overwhelming approval ratings among Republicans leading up to the primary election and ran uncontested—represented a prominent and credible source to the targeted voters. The call stressed three themes thought to be persuasive to Republican primary voters: (1) Willett’s conservative credentials, (2) Governor Perry’s long-standing support for him, and (3) Willett’s record as an incumbent.

Willet’s campaign conducted the automated calls between 10 AM and 3 PM on the day before the election, with the aim of placing recorded messages on voters’ answering machines. In the end, the automated call reached 85 percent of the targeted voters, either through an answering machine (54 percent) or a live answer (31 percent).

To measure the effect of the call on voter turnout, researchers examined both post-election individual-level and precinct-level data on the number of votes cast and the votes cast for Willett and Smith.

Results and policy lessons

Overall, the automated call program did not have significant impacts on the Willet-Smith race. The effect of the automated call appeared positive, but did not significantly increase voting turnout. Although Willett won the election, and there was some evidence that the automated call may have increased his votes relative to Smith’s, the call did not significantly improve Willet’s margin over Smith. 

While this was a low-cost intervention (each call cost about US$0.05), the cost-effectiveness of the automated call program depends on the size of its impact. Given that the automated call did not boost voter turnout or persuade voters to support a particular candidate, it may not represent a cost-effective strategy for communicating with and mobilizing constituents. But, the low cost of the program could facilitate opportunities for future research to explore other ways to enhance the effectiveness automated calls.

Shaw, Daron R., Donald P. Green, James G. Gimpel, and Alan S. Gerber. 2012. "Do Robotic Calls from Credible Sources Influence Voter Turnout or Vote Choice? Evidence from a Randomized Field Experiment." Journal of Political Marketing 11 (4): 231-245.