Tim Pawlenty’s poor showing last night is likely to trigger a few more weeks of wish-list speculation about new entrants into the GOP presidential field. While Rick Perry is the one who is a serious threat to run and potentially win, the guy who really makes Republicans swoon right now is Paul Ryan, the House Budget Chair.

But Ryan should stay put.

Ryan continues to loom large among Republicans, as Jon Chait notes today:

Ryan has come to dominate the Republican Party’s agenda and has personally become a totem -- a sort of mini-Reagan figure, frequently cited as credibility by others and never attacked.

But Chait’s conclusion – that Ryan should enter the presidential race and would immediately become the frontrunner – doesn’t follow.

Ryan, by running, would instantly diminish his status. Instead of an icon, he’d get in line with the rest of the gang in the cattle call. Suddenly, none of the other candidates would be praising him; indeed, it’s not unlikely that candidates currently willing to say nice things about his Medicare and budget ideas without fully endorsing them would get off the fence and actively turn against them. Questionable votes he took in the past (TARP, anyone?) would suddenly be raised just as often as his supposed courageousness is now praised. Serious People outside of the GOP who like him now would shy away once he was forced to spend time on abortion and marriage and the other things that Republican presidential candidates have to talk about (and there’s plenty of ammunition for them on purely budget matters, for whatever that’s worth).

Of course, running is a high-reward strategy…he could win! But it’s unlikely; Members of the House have traditionally been weak presidential candidates, and of course the main thing he’s known for, while a big plus in the primary fight, would be a huge liability should he somehow manage to capture the nomination. And running would at the very least jeopardize his House seat (I don’t know when the filing deadline in Wisconsin is, but even if he retreats in time running for president often is thought to spur a bit of backlash back home).

Ryan has a terrific gig right now. He’s respected, in his party and to a large extent within what remains of neutral Washington. He’s highly influential, perhaps the most influential Budget Chair ever – and if the Republicans do control a unified government after 2012, he’ll almost certainly be even more influential. Not, of course, as influential as he’d be as president, but even in the best of cases it’s still a longshot for him to be sworn into that office.

I think Ryan would be nuts to go for it.