On Saturday, Texas Gov. Rick Perry got into the race for the GOP presidential nomination, and within 24 hours, former Minnesota Gov. Tim Pawlenty got out.

Perry didn’t exactly chase Pawlenty out of the race; the Iowa straw poll (in which T-Paw finished a distant third) did that. But the two developments are closely related. They’re linked by the fact that Barack Obama is very beatable.

A lot of the preliminary autopsies of the Pawlenty campaign focus on two lines of argument. An explanation particularly popular among liberal pundits is that he was too ideologically moderate for the “extreme” GOP. The second line of thought is that he was too personally moderate, by which people mean he’s so dull he could bore a cat out of a tree.

Neither theory is baseless, but they’re both pretty weak. Mitt Romney is arguably even more boring than Pawlenty, and he’s leading the polls. Moreover, Pawlenty ran well to Romney’s right, on health care and even foreign policy.

The whole rationale for Pawlenty’s candidacy was that he could defeat Obama.

T-Paw often told audiences that on ideology there was little difference between him and the other candidates. What made him different, he explained, was electability. That’s a bad message for inspiring primary voters. And it’s a catastrophic message if you’re a bad candidate. When you run on electability, you better act like a really electable candidate. Instead, with his half-hearted jabs at Romney (It’s Obamneycare! No, it’s not! Yes, it is!), his graceless shots at Michele Bachmann and his seemingly manufactured passion, Pawlenty hardly looked like a general election juggernaut. Take electability away and you don’t even have a generic Republican.

And that’s important because over the last few months, President Obama has been losing to the “generic Republican” in the polls. In May, after the killing of Osama bin Laden, he had an 11-point lead against the generic Republican. By the end of July, it vanished as independents defected in response to a lousy economy and Obama’s feckless leadership during the debt debate. That Obama dropped below 40 percent approval in the Gallup tracking poll for the first time the same weekend Perry got into the race is telling, symbolically.

The “tea parties” breathed new life, and new controversy, into the so-called Buckley rule, named after the late William F. Buckley. Bill used to say he wasn’t for the most conservative candidate but the most conservative candidate electable. This practical principle was thrown out in several Senate races, including the disastrous nomination of Christine O'Donnell in the Delaware Senate race last year.

What’s both remarkable and dangerous about this fluid moment in presidential politics is that one can still remain loyal to the Buckley rule and support a very conservative candidate – at least for now. The weaker Obama gets, the more comfortable the conservative rank and file feel moving as rightward as possible. When the incumbent looks like a loser no matter what, electability loses its premium. That the GOP just swapped Pawlenty for Perry is testament to that fact, and far more significant than Bachmann’s straw poll victory.

(For the record, the straw poll is a really stupid fundraising stunt for the Iowa GOP. It’s primarily geared to candidates with support from one of two constituencies: the passionate and the easily bribed. Ron Paul’s second-place finish proves that it’s in no meaningful way a real poll, as his supporters are akin to “Battlestar Galactica” loyalists at a “Star Trek” convention, incapable of winning many converts and themselves unwilling to switch teams. Still, the straw poll is a fixture of the landscape, and candidates must deal with it.)

The danger isn’t so much that GOP voters will reject the Buckley rule but that they will think that almost any conservative will be electable given how weak Obama seems. After all, independents don’t subscribe to the Buckley rule – because they’re independents. If the economy improves or Obama gains traction, a Bachmann candidacy could resemble Goldwater ‘64 more than Reagan '80.

“Yes, people feel it now, the fire,” Bachmann proclaimed in a dramatic stage whisper Sunday night in Waterloo, Iowa. “They recognize that Obama can be beat.”

True enough, but fire is opportunistic. It doesn’t discriminate in whom it burns.

© 2011 Tribune Media Services, Inc.