Nate Silver recently posted an excellent analysis at his FiveThirtyEight blog on the degree to which approval ratings are predictive of presidential reelection prospects. While the state of the economy has consistently been shown to exert the largest influence on the outcome of U.S. presidential elections (along with a host of various other factors), economic indicators are also strongly associated with presidential approval ratings and thus public opinion polls of President Obama’s approval ratings can be helpful to guesstimate his odds of reelection in 2012.
Silver’s analysis is detailed and is worth a full look, but this is the key graph, based on data from the last 60 years of presidential elections:
Basically, it’s saying that approval ratings become more and more accurate predictors of reelection prospects the closer you get to the election. Right now we’re 21 months out from November 2012 and so Obama’s approval ratings aren’t very helpful in predicting his reelection prospects. However, by the time July rolls around, his approval rating may start to give us an early hint at whether or not he’ll be a one- or two-term president.
According to the graph, if his approval rating in July is at 35%, he’ll have a 40% chance or reelection. If he’s at 45% approval, he’ll have about a 57% chance of reelection. As of the end of January, his approval rating was at 50%, which if he maintains through July will give him a 70% chance of reelection. His reelection odds increase to 80% and 90% if his approval rating is at 55% and 65%, respectively. As the time between the polls and the election shrinks, the polls do an increasingly better job at predicting reelection.
The author of the analysis sums it up:
Much will change between now and then, of course. But Mr. Obama would probably win an election held next Tuesday — and that would not have been true a couple of months ago.