• His rivals are in trouble with the party's conservative base. Giuliani's support for abortion rights was highlighted in the first two debates, a problem in a party that still opposes abortion rights. McCain stood with Sen. Edward Kennedy, D-Mass., on an immigration bill widely reviled by conservatives as amnesty for illegal immigrants.

Romney's criticism of the immigration proposal — which is similar to one he supported a year ago — drew a sharp rebuke from McCain.

That, conservative strategist Greg Mueller said, was a mistake that helped elevate Romney as THE conservative critic of the unpopular proposal among the presidential candidates. "The McCain attack is the best thing that's happened to Romney since the day he got in," Mueller said.

He still faces formidable obstacles.

Foremost is the charge that he's a campaign convert to conservatism after running as a more moderate or liberal candidate in Massachusetts. Notably, he supported abortion rights when he ran for the Senate against Kennedy in 1994 and now opposes them.

"That could be his Achilles' heel," said David Johnson of Strategic Vision, which found in its new poll that Romney loses 4 percentage points of his support when voters are reminded that he supported abortion rights and gay rights in the 1990s.

"That's the one reluctance about Mitt Romney among conservatives," Johnson said. "They don't know if he's a true conservative."

The other potential challenge is his Mormon faith.

In Iowa, the recent Register poll found that 1 out of 5 Republicans said they were less likely to vote for Romney because of his faith. But Mueller suggested that social conservatives eventually would care more about what Romney would do in the Oval Office than what he would do in church.

"Is there an undercurrent out there nervous about the Mormon thing? Sure. But they really want to know where he stands on the issues they care about," Mueller said.

Romney's campaign aides say he can answer the flip-flop questions by pointing to his record as governor.

"The only position he's ever changed is on life, and he changed in the right direction," Romney's campaign spokesman Kevin Madden said. "It was a matter of him recognizing he was wrong in the past and now he's right on the issue."

Madden also said that Romney's faith faded as an issue when people met the candidate and realized that he "shares the same hopes and aspirations that Americans of many faiths do."

In the end, those close to Romney tamp down any talk of his being the front-runner, perhaps fearful of raising expectations too high and setting him up for a fall if and when the polls in those early states change again.

"It's still fluid. I expect they will change," Madden said.

But he said the key to Romney's success of recent weeks and his hopes for the coming months were the same: that people get to know him and his record — and that they like him.