Expert Commentary

Evaluating the impact of vice presidential selection on voter choice

2010 study from the University of California, Irvine, on the average effect a vice presidential candidate has on the electorate.

The selection of Rep. Paul Ryan as the 2012 Republican vice presidential candidate has prompted heated discussion around a perennial media topic: How much does the VP pick really matter in an election? Though there has been much loose speculation, some media analysts and political scientists have focused on more empirical aspects of the question. In any case, it is exceedingly difficult to separate out the effects of a particular candidate from the “team” with which he or she is running — to weigh precisely, for example, how a candidate might turn off independents but excite the party base — and few studies have been done in this area.

A 2010 study from scholars at the University of California, Irvine, “Evaluating the Impact of Vice Presidential Selection on Voter Choice,” provides a different lens through which to see this question. The study, published in Presidential Studies Quarterly, analyzed data from the American National Election Survey over the period 1968-2008; it examined voters’ specific preferences for both president and vice president and found that about 11% of the population on average has “conflicted” preferences — where a voter prefers the presidential candidate of one party but likes the vice presidential of the other party. Using this data, they estimate the degree to which a vice presidential candidate alone might influence the election outcome. The scholars note that this pattern of “conflicted” voting has diminished over time: only 6.9% and 6.8% of the populace had conflicted preferences in 2004 and 2008, respectively, likely the result of “increasing partisan polarization.”

The study’s findings include:

  • The net effect of a vice presidential candidate is generally less than 1% in terms of getting voters to cross party lines: “Only in 1972 was more than 1% of the final vote affected by conflicted vice presidential and presidential preferences; on average, over the 1968-2008 period, the net impact of conflicted presidential and vice presidential choices is only slightly less than 0.6% of the votes shifted.”
  • Though the selection of Gov. Sarah Palin is assumed to be a decisive factor in the defeat of Sen. John McCain, the study finds otherwise: The “gross impact of vice presidential selection in 2008 was very similar to (though slightly lower than) the historical average impact, and that the net impact of vice presidential selection in 2008, at about one-half of a percentage point, was also slightly lower than its historical average, may violate the common wisdom that Palin’s choice had significant electoral implications for McCain.”
  • On average, the patterns of “conflicted” voting has favored Democrats, as historically there have been more registered Republicans who have preferred the Democratic vice presidential nominee.

The scholars caution that there are two important caveats to their findings: The data “may understate the impact of vice presidential selection on choice because voters modify their views of the president based on vice presidential selection, and thus the data we report may be ‘contaminated’ by unmeasured effects of vice presidential choice. Second, mobilizing effects of vice presidential choice vis-à-vis turnout or campaign contributions or campaign activism are not reflected in our measures. For example, the selection of Sarah Palin was widely credited in the media as having motivated a Republican base that did not find McCain that attractive a candidate.”

Tags: elections, presidency