The chances of a default on the United States debt are still fairly small. The prices for credit default swaps, financial instruments that pay investors in the event that a default happens, imply just a 0.05 percent chance, or 1-in-2,000, of a default occurring within the next year, according to The Wall Street Journal.

That seems like a considerable underestimate of the chances — I don’t have much confidence that Wall Street does a competent job of pricing in political risk. But Congress still has ample time to prevent one by raising the debt ceiling, and the Treasury Department may use any and all means to stave off a default for as long as possible even if Congress fails to act.

Even if an actual default is unlikely, the possibility of one may nevertheless influence both sides’ bargaining positions. In addition, far more likely than an actual default are situations where we stop short of one but nevertheless have significant consequences for the American economy because of downgrades to the United States’ credit rating, severe reductions in government spending and significant anxiety in the market. So although we’ve touched on this subject before, it’s worth revisiting: what happens to American politics if the debt ceiling isn’t raised by Aug. 2 and the economy suffers as a result?

Let’s keep in mind that there are three basic possibilities:

1) The situation plays out in such a way that is harmful to President Obama and helpful to the Republicans on balance. 2) The situation plays out in such a way that is harmful to Republicans and helpful to Mr. Obama on balance. 3) The situation plays out in such a way that is harmful to both Mr. Obama and the Republicans.

What do I mean by the third possibility? A literal interpretation would be that Mr. Obama loses the White House, either to a Republican or (less likely) to an independent candidate. But the Republican Party loses its majority in the House. Maybe quite a few Democratic incumbents in Congress also lose.

More broadly, it would mean that any victories achieved in 2012 would be superficial and Pyrrhic. The public would not trust either side to carry out its agenda. The next several election cycles would be extremely volatile. Prospects for independent candidates for president and for third parties, whether emerging from the center of American politics or from the wings, would improve significantly. And within the major parties, power would tend to transfer away from those who hold it.

Whether you’re Barack Obama or John A. Boehner, or a Republican senator in a swing state considering how to vote on the debt ceiling, two out of the three possibilities are bad for you. Those are terrible odds. This is why I’m deeply suspicious of claims that either party to the negotiations believes it could benefit from a default. This isn’t a zero-sum game, and although politicians are bad at many things, they are usually fairly perceptive about what will enable them to hold onto power.

But suppose that you have to pick between the first two possibilities: one side loses and the other side “wins.”

Arguing for the “Obama loses” side is the political scientist John Sides:

Assume there is no deal and then assume, as [Treasury Secretary Timothy F.] Geithner and others have warned, that there are serious consequences for the economy when the debt ceiling isn’t raised. This will hurt Obama. And it will hurt him more than it will hurt the Republican Party. Presidents suffer the consequences of a bad economy. Divided government does not change this. Beware pundits who see silver linings for Obama in this scenario.

And arguing against Mr. Sides are Jonathan Chait of the New Republic and Ezra Klein of The Washington Post. Here’s Mr. Chait:

It seems highly plausible to imagine that, if the Republicans block a debt ceiling increase, that the public will turn on them. The business elite will decide that the Republicans are dangerous and must be stopped. Obama will use his bully pulpit to explain to the public that the Republicans have forced withholding of entitlement payments and the closing of vital government services. Quite possibly, this effect could overwhelm any actual economic ramifications. I know the models say the economy will be all that counts. That could be right. But the models have never seen anything like this before.

I’m more inclined toward the argument advanced by Mr. Chait. I don’t think I’d say that Mr. Obama would be likely to benefit politically — but I do think it’s anybody’s guess, and the empirical models that Mr. Sides references tell us very little.

Part of the reason for my skepticism is that I think these empirical models are, in general, a little bit overrated by the political science community. Some models claim to explain as much as 90 percent of voting behavior based on economic fundamentals and a few other variables. But the models suffer from profound theoretical flaws owing to the infrequency of presidential elections, and their predictive power is nowhere near 90 percent when applied to new (“out-of-sample“) cases. A cynical view is that the models are really just anecdotal arguments in quantitative dress: if a model has trouble explaining a particular election, you invent a new variable to excuse it. A fairer view, perhaps, is that the models do a good job with the “normal” cases — clearly the economy matters quite a bit to a president’s re-election chances — but fumble on the more difficult ones.

Whatever else the 2012 election would be if the debt limit is not raised in a timely fashion, it would not be a normal case. There’s no especially appropriate precedent for the economy tanking by such an immediate and direct result of action (or inaction) in Washington. One reason the public tends to score strong economic performance in favor of the president, and poor economic performance against him, is because the United States economy is incredibly complicated — it’s hard for the public to discern cause and effect. (It’s also hard for economists!) So the heuristic of blaming the president for poor performance and crediting him for strong performance is as reasonable as anything.

This would be different, however. The stock market could drop by thousands of points. Some major corporations, particularly in the financial services sector, might go under. Although the consequences might take some time to filter through the broader economy, there would nevertheless be a number of immediate and extremely visible effects. Many voters would feel as though they had perfectly reasonable grounds to connect the dots.

You’d have to weigh two things against each other: the additional damage to the economy, which is bad for the president all else being equal, and the additional ownership of the economy that Republicans would take for it, which is bad for them all else being equal. I don’t know which effect would win out, but it’s not a risk that either side should feel happy about taking.