Why do so many Republicans find it inexplicable that, given the current economy, Barack Obama has a solid chance to be reelected?

As Ezra Klein notes today, there’s a wide gulf between what many Republicans (and some independent pundits) think the fundamentals of the economy predict and what political scientists think the fundamentals of the economy predict. That is, the models devised by political scientists, economists, and Nate Silver tend to show a close race, not a GOP landslide (see also Joshua Tucker).

So why don’t Republicans know that?

I think there are two answers. One is that many Republicans appear to suspect academic political science, assuming that it must be biased against them. At least, it’s certainly my strong impression that, say, the premier political-science group blog the Monkey Cage gets cited a whole lot less often by the National Review than it does by the New Republic.

The other is a perception bias. The economy has been lousy compared with how it looked in 1984 but it’s nowhere near as bad as it was in 2008. (Matt Ylgesias has some relevant numbers.) Republican voters, however, don’t see things that way.

Gallup constructs an economic index based on two questions: one about economic conditions now, and the other about whether the economy is improving. It spiked up last week during the Democratic convention, reaching close to its post-recession high (still a negative number, at minus-18). Yet Republicans’ average perception of the economy, at minus-59, is basically where the nation as a whole was in September 2008, in the midst of the collapse.

Now, one has to be careful with these numbers, because they don’t allow for intensity, but the bottom line is that Republican voters believe the economy is bad and getting worse, while everyone else believes more or less what the economic data say: The economy is mediocre, but far better than in late 2008. See also Pew’s very similar findings.

I have no idea whether Romney campaign operatives and Republican pundits agree with GOP voters about the basic condition of the economy, but I wouldn’t be surprised if they do, at least to a fair extent — after all, they’re probably getting a lot of their information from the same places. At any rate, either they too think the economy is awful, or they’re spending most of their time addressing people who think that, which is bound to affect the way they talk about it.

All this means that many Republicans probably know less about what political scientists say about the effects of the economy on elections, and they also may hold an unrealistically negative view of how the economy is doing. This explains why they’re just so puzzled by Romney’s failure to open up a big lead over Obama.