It's like clockwork. Whenever a liberal columnist gives off even the slightest hint of violating progressive orthodoxy they get absolutely blasted by readers, and as sure as the sun will rise in the East that pundit's next column will contain some sort of modification or qualification, inevitably packaged in an unhinged rant against the right. You see this pattern somewhat frequently with Richard Cohen, and to a lesser extent with guys like Tom Friedman and E.J. Dionne.

One person you never see it happen to is Paul Krugman, because he's so consistently, rabidly anti-Bush and anti-Republican. Last week, however, Krugman wrote about "some uncomfortable facts about the economics of modern immigration, and immigration from Mexico in particular."

Krugman stated up front he was "instinctively, emotionally pro-immigration" but went on to acknowledge that low-skill immigrants threaten to "unravel" the social safety net and that "realistically, we'll need to reduce the inflow of low-skill immigrants" with "better controls on illegal immigration."

Even though Krugman took a few gratuitous partisan shots, the column was noticeable for its attempt to deal, at least in part, with some of the realities of a very complex, difficult, and emotional issue. Mickey Kaus noticed it too, commenting that "Krugman is clearly way off the PC/Dem/elite legalization reservation here."

Indeed, judging by the opening of his column today (Times $elect), Krugman seems to have been threatened with being excommunicated from the Upper West Side cocktail party circuit:

For now, at least, the immigration issue is mainly hurting the Republican Party, which is divided between those who want to expel immigrants and those who want to exploit them. The only thing the two factions seem to have in common is mean-spiritedness.

Nothing like a vicious slander to reestablish your liberal bona fides and moral superiority. Krugman goes on to recast his argument and reiterate that "it's important to be intellectually honest, even when it hurts," but his column today is vastly different in tone from the one last week, with much more emphasis on his unequivocal support for total amnesty.

So it looks like Krugman has more or less paid the penance for his little indiscreet episode of independent thinking. It must have been a nervous few days at Princeton fielding the angry phone calls and emails from fellow members of the progressive intelligentsia.