The Campaign to Defeat Barack Obama will launch a major ad campaign in Iowa accusing Mitt Romney for being a flip-flopping liberal in disguise.

The group has a long version of the ad, titled "Liberal Mitt's greatest hits," with clips of Romney taking positions that are anathema to many conservatives today.

Spokesman Ryan Gill described the initial video as a "roadmap" for the ads that will be aired, and said the group will run a six-figure ad buy in Iowa on cable and broadcast television to knock down Romney's numbers there and damage his "inevitability argument."

Gill said that the group is likely to expand the effort to attack Romney in other early-voting states including New Hampshire and Nevada, although the size of those ad buys is contingent on fundraising.

"Right now we’re just going to focus on our Stop Mitt Romney effort. Our analysis of the field is he’s the guy who’s not acceptable to conservatives but is displaying this ability to get the GOP nomination and risk what we had last time around with John McCain," said Gill.

The laundry list of video clips include Romney promising to "protect a woman's right to choose," saying he was "an independent during the time of Reagan-Bush" and doesn't want to return to their policies, that he supports affirmative action, reducing greenhouse gas emissions, the Wall Street bailout, some gun control legislation, and a path to citizenship for undocumented immigrants.

A shorter version of the ad hits Romney for many of these positions. "Mitt Romney's so liberal he's fought conservatives on abortion, RomneyCare, bailouts, illegal immigration, and much more," says the narrator.

The former Massachusetts governor has been held at arm's length by many Tea Party supporters and other conservatives. But in the latest poll of Iowans, and in national polls, he continues to lead by holding down centrists while the other candidates divide up the conservative vote.

Watch the longer web ad here: