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Post-Convention Bounces: A Taxonomical Guide

With Romney’s address closing the RNC, preparations for the quadrennial bouncefest are well underway. Most discussion will focus on the size of each candidate’s bounce, but there isn’t a strong correlation between a large bounce in success in November. In this political environment, there’s more to follow than simply whether the candidates meet or exceed historical expectations. It’s also worth tracking the share of the vote that each side receives at their post-convention peak—especially in an election where the public has hardened views about the incumbent.

This is a largely unscientific inference from past conventions, but voters who choose to align themselves following the conventions are probably likely to vote that way in November, since voters already hold unusually well defined and durable views about the president. How many people going to vote for Romney—which probably entails deep dissatisfaction with the president’s performance—but tell a pollster that they’re voting for Obama after his convention? Or conversely, how many people that feel comfortable declaring their intent to vote for Romney after months of negative advertisements will decide to vote for Obama in a couple of months? My hunch is that very few voters will fall into these category, and it’s my suspicion that’s what happened in 2004. In this model, conventions represent rare clarifying moments when reluctant and undecided voters are momentarily willing to offer their support to the candidate that they’re likely to vote for in November, even if temporarily.

So how should we interpret the bounce? For starters, the bounce could help address the core and unresolved question of this election: whether 50 percent of voters are currently prepared to dismiss or reelect President Obama. One side, primarily consisting of Romney supporters, contends that Obama’s approval ratings are beneath fifty percent and, therefore, the electorate is simply looking for a plausible alternative to turn the country around. Democrats contend that a majority of voters like the president and haven’t necessarily judged him as a failure, even if they’re disappointed by his performance. Both explanations are supported by the data, but if Obama exceeds 49 or 50 percent of the vote following the DNC, that should be interpreted as a solid sign that a majority of voters are willing to reelect the president. And similarly, if Romney could reach 49 or 50 percent without a similar showing by Obama, that would highlight Obama’s vulnerability.

What if neither candidate approaches 49 percent? As a general rule, the incumbent’s share of the vote is more predictive than the challenger’s peak, so if Romney doesn’t near 49 percent after his convention, that wouldn’t preclude him from such a showing in November. Many voters with deep reservations about the president’s performance could justifiably hold out for more information about Romney before choosing to support him. On the other hand, if Obama can’t inch close to 49 percent, that could be a more significant sign that a majority of voters have very deep reservations about giving him a second term. Again, it wouldn’t outright prevent him from winning, but it would contradict the view that the voters who like him but are disappointed with Obama’s performance are itching to join his cause in November. However, if one candidate gains a decidedly higher share of the vote at the peak of their bounce, that would be a very good sign for that candidate, even if they fall short of 49 percent. The candidate with the highest peak has won 10 of 12 presidential elections since 1964, including every election involving an incumbent president.

If Obama exceeded 49 or 50 percent of the vote after his convention, it would be a very good sign for his chances, demonstrating that he probably has the voters necessary to prevail in November. If neither candidate inches near 49 percent, it would be a sign of a genuinely close and competitive race. And if Romney can momentarily consolidate a near majority of voters or Obama falls well short of 50 percent, it would indicate that the country is prepared to act on their disappointment with the president’s performance, even if it remains to be seen whether Romney can capitalize. New information, the debates, or external events could plausibly invalidate the lessons learned from post-convention polling. And the narrow window between conventions could dull Obama’s bounce or prevent Romney from fully realizing his own. But with the electorate harboring entrenched views, it could be quite telling if either candidate secures a meaningfully larger share of the electorate at the peak of their post-convention bounce.