The former Massachusetts governor had focused on his business credentials and played down his ideology, four years after he failed in his attempt to win the GOP nomination by running as a social conservative.
"I was a severely conservative Republican governor," Romney told the Conservative Political Action Committee's annual gathering Friday. It was a speech that, advisers said, Romney viewed as an important chance to speak directly to the conservatives who rejected him in three contests Tuesday.
He insisted that he is a conservative in both record and background, trying to persuade the GOP's skeptical right flank that he is acceptable as the party's nominee.
"My path to conservatism came from my family, from my faith and from my life's work," Romney said.
He's working to gain trust from the activists who make up the GOP base and who drive the party's primary contest. They view him skeptically because of his past shifts on a variety of issues, including his previous support for abortion rights.
Conservatives generally view Romney's chief rivals, Santorum and Newt Gingrich, as having views more in line with their own.
Romney's new message comes as he's trying to prove he can win over a broad spectrum of Republicans. He has yet to win the majority of GOP votes in any of the contests so far. And he's looking to emerge strongly from Super Tuesday, March 6, when 10 states have nominating contests.
In offering the defense, though, Romney drew attention to the problem he's faced throughout the primary contest.
"I've never heard anybody say, 'I'm severely conservative,' " conservative talk radio host Rush Limbaugh said Friday.
Romney's conservative opposition remains divided -- the former House speaker has won one state and the former Pennsylvania senator four. But Santorum is suddenly threatening Romney's dominance in states where his team had previously felt comfortable.
Last week, Santorum won contests in Minnesota, Missouri and Colorado. While Romney's team decided not to compete in Missouri's nonbinding primary and acknowledged early that Minnesota might pose problems, they were much more optimistic about Colorado. Romney spent several days campaigning there ahead of the caucuses, but his team spent just $32,000 on TV ads in the state.
In a sign it's nervous, Romney's team abruptly added campaign events in Maine, including a town hall Friday night where he took questions from voters. Saturday, Romney narrowly won the state's caucuses.
Romney's team is preparing an aggressive push against Santorum in Michigan, where Romney was born, is a household name and where his advisers had hoped for an easy victory. Romney's father, George, served as governor of Michigan and chairman of American Motors Corp. before mounting a failed bid for president in 1968.
Romney all but ignored Santorum ahead of this week's contests. Advisers say that will change, with Romney taking on Santorum's record on union issues during his time in the Senate from heavily unionized Pennsylvania.
Santorum joined a filibuster of a national right-to-work act and voted to defend legislation that sets pay for public sector workers. He defends that record as an issue of states' rights.
Romney has also planned a more aggressive campaign schedule in Michigan in the coming weeks. He plans to stop in Grand Rapids on Wednesday and the Detroit area on Thursday, and stay in the Midwest through the end of the week. He's likely to spend some time campaigning in Ohio, which holds its primary on March 6, and is the second Rust Belt state to hold a nominating contest.
Romney's big advantage is money. He and his allies, the super PAC Restore Our Future, have spent a combined $25 million on TV ads to date, helping to drive wins in New Hampshire, Florida and Nevada. That dwarfs the $7.1 million Gingrich and his allies have spent on airtime and the $2.5 million Santorum backers have shelled out.
Still, Romney is facing a crush of primaries and caucuses on March 6, when his financial edge will be tested. But he always could add to that himself. He hasn't said if he'll contribute any of his considerable personal fortune to the campaign. In 2008, he spent $45 million.