Rick Santorum says Mitt Romney is a "bland, boring, career politician who will lose to Barack Obama" -- talk about an ingrate.
Santorum's criticism came despite his acceptance of a $10,000 contribution in 2006 from a political action committee controlled by Romney.
Romney's "Commonwealth PAC" sent then-Sen. Santorum the donation in an attempt to gain support among leading conservatives ahead of Romney's 2008 presidential campaign. At the time, Santorum was locked in a tough re-election battle in Pennsylvania.
Santorum finished a mere eight votes behind the GOP frontrunner in the Iowa Republican presidential caucuses Tuesday and is hoping to keep up his unexpected momentum. Santorum made the comment in a recent fundraising solicitation.
Santorum threw his support behind Romney in 2008 -- an endorsement he has since tried to walk back, defending it as a move to stop the nomination of Sen. John McCain of Arizona, the eventual GOP nominee.
In a dizzying twist, McCain joined Romney Wednesday to announce his support for the former Massachusetts governor. McCain's appearance was notable, given how acrimonious things were between the two men during the 2008 campaign.
And speaking of McCain, Restore Our Future, a so-called "super PAC" supporting the candidacy of former House Speaker Newt Gingrich, has gone negative -- sort of. Despite Gingrich's past exhortation to his supporters that they stay positive, the group featured "A Tale of Two Mitts," a McCain ad from 2008 mocking Romney for his flip-flopping on abortion and gun rights.
Winning Our Future, not to be confused with the pro-Romney "Restore Our Future," has not released a list of donors, nor will it be required to until the end of the month. Super PACs can raise unlimited amounts from corporations, individuals and labor unions and use the funds to elect or defeat candidates.
The contribution may have gotten Santorum to take Romney's side, albeit temporarily, but it didn't help much in the election. Santorum was thumped by now U.S. Sen. Bob Casey, his Democratic opponent, by 17 points.
John Dunbar contributed to this report.