News Release

Study finds political campaigns may change the choices of voters – but not their policy views

Peer-Reviewed Publication

Oxford University Press USA

A new paper in The Quarterly Journal of Economics, published by Oxford University Press, measures the overall impact of electoral campaigns and finds that televised debates have little effect on the formation of voter choice. Information received from other sources such as the media, political activists, and other citizens, matters more.

Researchers and pundits have long debated the impact of political campaigns. One view is that the weeks immediately preceding elections are a crucial period. Campaign information can help voters assess the performance of incumbent politicians, compare the qualities and positions of all candidates, and perhaps even reconsider their policy preferences. But some researchers argue that campaigns have minimal effects because most people decide on their candidate long before the election.

Researchers here used survey data from 62 elections in ten countries (Austria, Canada, Germany, Italy, the Netherlands, New Zealand, Sweden, Switzerland, the United Kingdom, and the United States) since 1952 to study how voters make their choice. The data included 253,000 observations. The authors looked at the difference between whom voters said they said they would vote for, before the election, and whom they said they voted for, after the election.

The investigation revealed that the fraction of people with identical vote declarations before and after the election increased by 17 percentage points over the 60 days leading up to the election, from a baseline of 71%. On the last day before the election, 12% of voters still do not know (or will not say) whom they will vote for or state a different vote intention than their ultimate choice. In total, 17% to 29% of voters make up their minds during the last two months of campaigns. This large increase in individual vote choice consistency is associated with a 5-percentage point reduction in the distance between predicted and final vote shares: voters who make up their minds in this period significantly affect the electoral results.

Within a given election, younger and less educated voters are more influenced by campaign information, and voters who identify strongly with a party are less so. Changes in vote choice are driven by changes in voters’ beliefs on the candidates’ positions and qualities as well as changes in the issues voters find most important. By contrast, their policy preferences remain stable throughout the campaign.

The researchers here also investigated evidence on the relative importance of different sources of information. Information from televised debates had little effect on voter decisions. Shocks such as natural and technological disasters, which occur independently of the campaigns, did not appear to change voter decisions either. These results suggest that information acquired throughout the campaign from sources like news stories or friends is more important.

The authors were surprised to find that TV debates – for all the interest they generate, the large viewing audience they draw, and the many media commentaries they provoke – do not appear to change voting behavior. Overall, the results suggest that even if voters sometimes seem relatively uninformed and uninterested, their vote choices actually depend on extensive information beyond just debates.

“Since our data cover 62 elections, they enable us to compare the importance of electoral campaigns in different settings,” said the paper’s lead author, Vincent Pons. “Campaigns play a decisive role in all periods and all countries we study. But interestingly, the fraction of voters changing their minds in the last two months before the election is much smaller in the U.S. than in Canada, Germany, New Zealand, and all other democracies in our sample.”   

The paper “How Do Campaigns Shape Vote Choice? Multi-Country Evidence from 62 Elections and 56 TV Debates” is available (at midnight on March 2) at:

Direct correspondence to: 
Vincent Pons
Associate Professor of Business Administration
Harvard Business School
Morgan Hall 289 Soldiers Field
Boston, MA 02163

To request a copy of the study, please contact:
Daniel Luzer

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