I guarantee this switch will hurt Michele Bachmann a lot more than Kent Sorenson’s betrayal yesterday.  At least Sorenson didn’t make a half-million-dollar ad buy for Ron Paul on his way out the door:

A political action committee which had planned to support Michele Bachmann’s presidential campaign has very quietly defected to Mitt Romney — and it’s spending big on his behalf.

Citizens for a Working America, the so-called Super PAC which aired TV ads against a Democratic congressional candidate last year, had indicated earlier this year that it was backing the Minnesota congresswoman in the GOP nominating contest. But the group instead made a $475,000 Iowa ad buy on Christmas Eve in support of Romney, according to Federal Election Commission data published today.

The so-called independent expenditure was listed as supporting Romney’s candidacy, and an Iowa political operative who has seen the ad confirmed to The Daily that it’s a 30-second positive spot about the former Massachusetts governor that doesn’t mention any other candidate.

Just four months ago, the Washington Post heralded this group as a “major Bachmann super-PAC” in the post-Ames coverage, although it’s not clear whether CWA ever spent any money on Bachmann’s behalf.  Look  at the conservative brain trust in this group that originally backed Bachmann:

A trio of well-known conservatives have organized a so-called “super PAC” to aid Minnesota Rep. Michele Bachmann’s bid for the Republican presidential nomination, according to sources familiar with the move.

Citizens for a Working America, as the group is known, will be chaired by former Ohio Secretary of State Ken Blackwell. Ed Brookover, a longtime political consultant and adviser to Bachmann, will be involved as will conservative lawyer and economist Marc Nuttle.

“Michele Bachmann is a principled conservative with the policy prescriptions our country needs to pull out of its economic doldrums,” said Brookover in an email exchange with The Fix. “We look forward to promoting her and her programs to the American public.”

The group was formed in the fall of 2010 and spent more than $250,000 to defeat former South Carolina Democratic Rep. John Spratt. It will now be turned entirely to aid Bachmann. It joins “Keep Conservatives United”, a super PAC formed last month with the express purpose of helping Bachmann win the GOP nomination.

Ken Blackwell was a darling of the Right a few years ago when he helped push through a ban on same-sex marriages in Ohio in 2004, then ran for Governor of Ohio two years later, losing to Ted Strickland.  Blackwell later joined the conservative Family Research Council, where he remains as a senior fellow.  However, Blackwell apparently left the group a couple of months ago when he switched his personal endorsement to Rick Perry, just as Perry’s bubble deflated entirely.  It looks as though Blackwell’s former campaign manager Norman Cummings may be running the group now. The Hill reported yesterday that Ed Brookover left CWA but still backs Bachmann, and is somewhat bemused by the sudden switch:

The group originally counted longtime Bachmann adviser Ed Brookover and former Ohio Secretary of State Ken Blackwell as active board members. But Blackwell endorsed Rick Perry in October and Brookover told The Hill that he left the group a while back.

“They weren’t raising any money for the Michele effort,” he said. “I have no idea why [they are spending for Romney]. I’m still supporting Michele.”

In some ways, this switch makes more sense than Sorenson’s to Paul.  Bachmann went toe to toe with Paul in the debates on foreign policy, especially in the last two, where the exchange got heated.  Paul later accused Bachmann of “hating all Muslims” while on the Tonight Show with Jay Leno.  It’s a little mystifying how Sorenson can square the circle between those two diametrically opposed positions and claim to have supported both of them in the same cycle.  On the other hand, Bachmann never really went after Mitt Romney in debates in the same way she attacked Paul, Newt Gingrich, and Rick Perry, a dynamic that had been noted more than occasionally over the last few months.  A switch by her super-PAC to Romney raises fewer issues of hypocrisy, although it still certainly looks … odd.  Why not Rick Santorum instead, who is much closer to Bachmann politically and is arguably catching a polling wave this month?

The loss of this super-PAC will erode both credibility and firepower from Bachmann in the last few days of the campaign in Iowa, and will boost Romney far more than Sorenson will do for Ron Paul.  It’s not a gamewinner by itself for Romney, but it looks like game over for Team Bachmann.