President Obama’s top campaign advisers redoubled their efforts Wednesday to chop down Mitt Romney, one day after the former Massachusetts governor won a very narrow victory in the Iowa caucuses.

The Obama team, which has repeatedly focused its early efforts on defining the GOP frontrunner, continued in that vein Wednesday with some of its most strident criticism yet. That criticism included labeling Romney the ”25 percent man” — a reference to his inability to rise beyond around one-quarter of the vote in GOP polls.

Obama adviser David Axelrod said Romney’s win in Iowa doesn’t change the fact that he has been unable to raise his stock in the polls.

“He’s still the 25 percent man, and until he proves otherwise, we can’t close the books on this nominating process,” Axelrod said.

Axelrod also accused Romney of calling in a super PAC to take down an ascendant Newt Gingrich.

Axelrod said the super PAC ran “undoubtedly the most brutal and negative campaign Iowa has seen.”

“Romney won the Iowa caucuses in part because he called in the Air Force in the form of his super PAC to carpet bomb Newt Gingrich,” Axelrod said.

The super PAC spent more than $3 million, largely on ads attacking Gingrich’s record. But it is not allowed to coordinate with Romney’s campaign, and there is no indication that Romney’s campaign violated that law by asking the super PAC to run the ads.

Obama campaign manager Jim Messina pointed out that Romney took about the same number of votes as he did when he lost the Iowa caucuses in 2008 and actually took a smaller percentage of the vote.

“After four years of constant effort ... Mitt Romney received fewer votes and a smaller share of the vote,” Messina said.

Romney supporters note that the former Massachusetts governor actually spent considerably less time and resources in the state than he did in 2008, only launching a full-scale effort there in recent weeks.

They say the Obama team’s focus on Romney reflects the realization that, more than any other candidate in the GOP field, Romney has polled neck-and-neck with the president nationwide.

“President Obama’s cronies spend more time strategizing about Mitt Romney than they do strategizing how to create jobs for the 25 million people who are out of work,” said Romney spokeswoman Andrea Saul. “For the near 9 percent unemployed – and the millions more who feel the country is on the wrong track – help is finally on the way. The campaign to defeat Barack Obama and get this economy working again has begun.”