We already knew this given the polls at the time, but now some political science professors at Bradley University are backing it up with more data.
Via Noel Sheppard at Newsbusters:
For over five years, a consistent media claim has been that former Alaska governor Sarah Palin hurt Republican presidential nominee John McCain in 2008 and that he would have fared better with anyone else on the ticket besides her.
A recent study by political science professors at Bradley University debunks this claim concluding instead that Palin was a net plus for McCain including with independents and moderates…
Burmilia and Ryan introduced their study:
In a recent issue of this journal, “The ‘Palin Effect‘ in the 2008 U.S. Presidential Election” by Jonathan Knuckey addressed a substantively interesting question: did the selectionof Sarah Palin negatively affect John McCain‘s share of the vote (Knuckey 2012)? In line withthe conventional post-election narrative and other research on the ?Palin Effect? (see Elis, Hillygus, and Nie 2010), the article concludes that Palin hurt McCain among key moderate andindependent voters. Specifically, the article makes three claims. First, Palin had a measurable, independent effect on the presidential popular vote in 2008. Second, she hurt the McCain campaign by driving away independent and moderate voters. Third, Palin is a uniquely divisive figure and her effect on the presidential vote was larger than any recent vice-presidential nominee.
Burmilia and Ryan debunked claim one:
The interaction term is not significant and there is no feeling thermometer rating for Palin that produces a negative and statistically significant slope on McCain vote choice for independents or moderates. In fact, the slope is positive, though not statistically significant for all Palin feeling thermometer values. For Republicans, any rating of Palin results in a statistically significant positive effect on McCain vote choice although there is no increase in effect size as a Republican rates Palin more positively. Excepting independents who are neutral toward Palin (near 50 on the thermometer), the positive effect of Palin rating on vote choice among independents is not statistically different from Republicans. The same is true for ideology. There is never a statistically significant negative effect of feelings toward Palin on McCain vote choice conditional on ideology. As before, there are no statistically significant differences between conservatives and moderates. The substantive interpretation is clear: the positive relationship between McCain vote choice and feelings for Palin is not conditional on party identification or ideology. Not only is there no negative effect for independent voters on feelings toward Palin, there is no meaningful difference between Republicans and independents on how feelings toward Palin affected McCain vote choice. Our analysis reaches a different conclusion from the original paper; we find that the positive relationship between the Palin feeling thermometer and the likelihood of voting for McCain does not depend on a voter‘s ideology or party affiliation. Therefore the results call into question the major conclusions of the paper; Palin did not have a negative effect on McCain‘s vote share overall, nor did she result in ?eroded support for McCain among critical `swing voters‘ such as Independents and moderates, (2012: 286-287).
The study’s conclusion:
Sarah Palin was a highly visible and polarizing figure in the 2008 presidential election. She generated media attention and attracted praise and criticism beyond what is usually given to vice-presidential nominees. It is logical to assume, as popular post-election wisdom did, that her impact on the outcome of the election was also greater than previous running mates. “The ‘Palin Effect’ in the 2008 Presidential Election” uses survey data to support that conclusion. Our reading of the article respectfully argues that the data do not support the key findings, which are:
1. That there is a negative conditional effect of feelings toward Palin on likelihood of a McCain vote among independents and moderates. We find that using marginal effects, as is appropriate for cross-sectional data, shows that Palin had a positive effect on McCain vote choice, and based on our model specification, may have had a positive, conditional relationship for independent voters.
2. That Palin‘s impact on vote choice was the largest among all recent vice-presidential candidates. We find that when confidence intervals are included, Palin‘s effect was not necessarily the largest among the nominees since 1972.
You can read the entire piece here.