A political action committee supporting Newt Gingrich sought to undercut GOP Sen. John McCain's (Ariz.) endorsement of rival Mitt Romney Wednesday by posting an attack ad from the 2008 presidential campaign cycle in which the Arizona senator accuses Romney of flip-flopping.

The Winning Our Future super-PAC posted the 2008 ad, in which Romney is shown with conflicting statements on a series of issues, on its website Wednesday and distributed the link to reporters.

Titled "A Tale of Two Mitts," the "Masterpiece Theater"-styled ad shows the former Massachusetts governor shifting positions on abortion and the Second Amendment.

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For instance, clips contrast statements Romney made during his Senate run — "I believe that abortion should be safe and legal in this country" — and his gubernatorial campaign — “I will preserve and protect a woman's right to choose and am devoted and dedicated to honoring my word in that regard" — with a claim in a 2008 debate that he had always supported abortion rights.

“Mitt Romney’s Flip-Flops Truly Are Masterpieces,” the ad says.

The group is not allowed to legally coordinate with the Gingrich campaign, but Rick Tyler, a former Gingrich aide who runs the group, says that they plan to engage Romney more directly now that the former House Speaker has shown a willingness to do so himself.

"We are currently planning the next phase of our messaging given our new expanded parameters. [Gingrich] is by far the best strategist we have so we listen to him, through the media," Tyler told CNN.

An incensed Gingrich has angrily blasted Romney as a "liar" and blamed a series of television ads aired by a pro-Romney political action committee for his disappointing fourth-place finish in the Iowa caucuses Tuesday night.

"Gov. Romney ran a relentlessly negative campaign of falsehoods," Gingrich told supporters in Concord Wednesday, noting that "three out of four Republicans rejected [Romney]" at the polls Tuesday night.