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Election day volunteer Vicki Groff places a sign to direct voters to a polling station at Kenilworth School February 28, 2012 in Phoenix, Ariz. What are the big economic indicators that could influence voters one way or another today? - 

Kai Ryssdal: You can measure economic stuff 'til you're blue in the face -- trust us, we keep track of it all. But if you're not measuring the right stuff, you're doin' it wrong.

Marketplace's David Brancaccio explores the politically relevant economic indicators.

David Brancaccio: Some political scientists call it the "holy grail" -- finding exactly which economic indicators accurately predict who'll become the next president of the United States. But with so many numbers to choose from, finding the right portfolio of possibilities is tough.

Political scientist Douglas Hibbs says, forget more common indicators such as GDP or unemployment. What makes a winner is personal disposable income in America coupled with current American war casualties.  He calls his model "Bread and Peace."

Douglas Hibbs: I probably cribbed it from Lenin.

Lenin's ingredients were bread and circuses. Hibbs says Iraq and Afghanistan won't be much of a drag on President Obama's chances compared to, say, Vietnam.  That leaves growth in disposable income as the decider.

Hibbs: I'm projecting out a growth rate of maybe 2 percent or just under.  I think that's the most likely scenario during this restrained phase of the recovery.  Puts him at a relatively narrow loss to the challenger.

A 52-to-48 loss for Obama is his call, no matter the challenger. But, again, Hibbs' model is just one of many and they can't all be right.

Sean Trende is the Senior Elections Analyst for RealClearPolitics. He says one reason any of these models seem to do OK is because they are tested after the fact, on elections past.

Sean Trende: If the president does win, people will say it is GDP and unemployment.  If he doesn't win, they'll say it's real disposable income. And that's all possible, but there's also a third possibility which is the correlation and not causation and it's really because Rick Santorum or Mitt Romney were terrible candidates and the president did a good job selling his health care bill in the stretch, we don't know.

Let's not forget even a fourth possibility: football. Take the Washington Redskins's last home game before a presidential election, when the Skins lose, the incumbent party tends to lose.

One more indicator for you: there's Intrade, a website where people bet on elections. Today, Intrade gives Mitt Romney a seven out of ten chance of winning. For what it's worth, that site got it right predicting that "The Artist" would win best picture at the Oscars.

In New York, I'm David Brancaccio for Marketplace.

Follow David Brancaccio at @DavidBrancaccio