I scoffed when some friends and colleagues speculated after Sarah Palin's well-received convention speech could have a major effect on the campaign in her running mate's favor. I also scoffed when some people I talked to claimed that Palin's much less well-received television interviews would be devastating to her ticket. The reason was simple. To oversimplify only slightly, political science research suggests that vice presidential choices have little effect on election outcomes. Indeed, despite what the priorities of media coverage might imply, campaigns as a whole have only a marginal effect on election outcomes (which can be explained with considerable accuracy by a few external factors, most notably whether the candidate in an incumbent and the condition of the economy.) History suggests the vice presidential choices might increase the chances that a candidate will win a running mate's home state, and otherwise matter very little. And since Palin came from 1)a small state that 2)was already solidly Republican, McCain's choice figured to have a negligible effect.
John Sides at the Monkey Cage, however, points us to a fascinating analysis of the 2008 campaign suggesting that I may have been wrong to dismiss the potential impact of a Palin pick so quickly. Political scientist Richard Johnston (author of the seminal study in voting behavior Letting the People Decide) and Emily Thorson (blogger as well as political scientist), have found data suggesting that the Palin choose may well have had a substantial impact on the 2008 election. Tracing McCain's approval ratings, the argue that it was Palin, not the economy, that explain's McCain's losing margin:
The failure of the economy to move the campaign is a puzzle in its own right. Election after election shows that perceptions of the economy are a crucial force shaping vote preference. Why then did events as terrifying as the meltdown not translate into electoral decisions? And if the meltdown did not drive the dynamics of the campaign, what did?
We think the answer to this question starts with Sarah Palin, and we base this judgment on the level of detail made possible by the NAES. John McCain’s August 29 announcement of Palin as his running mate surprised the Republican establishment, the media, and especially voters. She made a strong first impression: she enjoyed high approval ratings after her acceptance speech, and the percentage of voters saying that they intended to vote Republican skyrocketed. But within days of the speech, her ratings began a precipitous slide from which she—and the McCain campaign—never recovered. Throughout the rest of the campaign, vote intentions were closely tied to Palin’s approval ratings: each major Palin approval drop was followed, within a day or two, by a drop in McCain vote intention. No other factor moved McCain support with such precision. Comparison of the correlation between running mate approval ratings and vote intentions from 2000 and 2004 confirms Palin’s peculiar importance in 2008.
Of course, as Johnston and Thorson acknowledge, the data is merely suggestive; it cannot prove that Palin had an unprecedented effect on the 2008 elections. But, at the very least, it means that we cannot easily dismiss claims that vice presidential selections may be more consequential than past elections have suggested. What this also means is that political scientists, when studying elections, always have to be modest in their conclusions, for an obvious reason: the relative rarity of presidential elections means that we have to draw conclusions based on relatively small samples, often encompassing very different historical eras. Particularly given that there are many ambiguities in analyzing individual elections as well, it's important not to be too confident that past historical patterns will recur. After all, even if the previous consensus of the research was correct, history can change. Even if vice presidential choices had little impact in most past elections, they may matter more in the future for reasons we can't fully identify yet.