Romney rolled to a 14.5-percentage-point victory in Florida and left Gingrich's campaign strapped for cash, yet only a week ago the former governor was criticizing the former House speaker.

"Speaker Gingrich and Senator Santorum have over half a century's worth of time in Washington between them. They can't fix our country's spending problem because they helped create it," Andrea Saul, a Romney spokeswoman, said last Wednesday in a statement.

The comment came a day after Santorum swept Romney in three state primary races where Gingrich garnered low numbers. Romney's camp has likely crippled the former speaker's campaign, but there's always the worry that Santorum and Obama will pick up the private equity storyline and use it in different or similar ways against Romney. No matter how hard he tries to disregard that past, Romney's opponents will likely use his business record against him.

Santorum is the latest challenger to question Romney's commitment to conservatism. The former senator released an ad that touts his "full-spectrum" conservatism on Tuesday.

"A full-spectrum conservative, Rick Santorum is rock-solid on values issues, a favorite of the Tea party for fighting corruption and taxpayer abuse, has more foreign policy credentials than any candidate and Rick's made-in-the-USA jobs plan will make America an economic superpower again," the ad said.

As the video runs, two printed quotations run at the bottom of the advertisement with critical remarks about Romney. "Among national voters Santorum now runs slightly stronger against Obama than Romney," one quotation from Rasmussen Reports says. Then a Jan. 9 Wall Street Journal article is quoted: "Overall, we'd score Mr. Santorum's economic agenda as bolder than Mr. Romney's."

Santorum has used his three victories from last Tuesday as newfound authority to hurl attacks at Romney in order to win hesitant Republicans.

Romney ramped up his conservative rhetoric at the Conservative Political Action Conference in Washington last Friday and used it as a platform to convince the GOP base of his allegiances.

Romney has been unable to shake concerns that he is a moderate northeastern politician. If Romney wins the nomination, he must keep enthusiasm among Republican-base voters, because they're a critical foundation to upsetting the incumbent president.

Even if Santorum and Gingrich and every other conservative standard bearer endorses Romney in the general election, the former governor would still have to hope it's enough to motivate GOP turnout.

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