What do the GDP numbers tell us about the presidential election?

The new numbers on 2nd quarter growth in gross domestic product came out this morning, showing that the economy grew at a 1.5 percent annual rate in the 2nd quarter. They're the sort of economic figures we've come to expect of late -- not a recession, but pretty far from robust growth. But what can they tell us about the 2012 presidential election?

Well, if you average GDP growth over the first two quarters of election years going back to 1948 and use it to predict presidential vote shares, you get this:

Now, this isn't the strongest correlate with presidential vote shares. Real disposable income does a bit better, as do measures that incorporate third quarter growth. But still, by itself, this measure explains 39% of the variation in vote shares.

You'll notice that there's a red dotted line projecting the 2012 presidential vote based on GDP growth this year (an average of 1.75%). It basically hits the trendline right at 50%, continuing to indicate a really, really close contest. Notably, we're experiencing slower economic growth than George W. Bush had to contend with in 2004 or his father faced when he lost reelection in 1992.

Of course, I'm not making a forecast (political scientists are apparently terrible at that). I'm just suggesting that what we've seen so far this year from the economy is consistent with a very close election, and that things with more modest influences on the vote (campaign spending, voter turnout efforts, new voter ID requirements, etc.) could end up making all the difference.

And all of this will matter more than Obama telling you you didn't build something or Romney trying to reprise Billy Bob Thornton's role in "Love, Actually."