Romney has assembled prominent advisers, but he now adopts views that even they are uncomfortable with. He calls Obama a dangerously weak president abroad, but Robert Kagan, his neoconservative foreign-affairs adviser, has indicated he's comfortable with much of Obama's program (the president has adopted the thesis of Kagan's latest book, The World America Made). Romney has also come close to calling for war with Iran, decried Obama's withdrawal from Iraq and his "massive defense cuts," and opposed negotiating with the Taliban -- all of which suggests that a President Romney would be another first-term George W. Bush.

Romney pledges to designate China as a currency manipulator and slap on tariffs -- ensuring a trade war -- "on day one of my presidency." He opposes government help for housing, even though one of his chief advisers, Glenn Hubbard, has written an ambitious plan to reduce interest rates on mortgages. "It's fine academic work, but it's not anything that anyone [on the right] could touch," says Douglas Holtz-Eakin, McCain's adviser in 2008, explaining that the Tea Party was ignited by a rant by CNBC's Rick Santelli against bailing out mortgage holders. "No element of it is politically feasible."

And the primary race is still impelling Romney further from his gut instincts. Asked whether he would fight Obama's contraceptive-insurance mandate, he first said, "The idea of presidential candidates getting into questions about contraception within a relationship between a man and a women, husband and wife, I'm not going there." An hour later, he went there. Romney spokeswoman Andrea Saul "clarified" his answer, claiming "The way the question was asked was confusing. Governor Romney supports the Blunt bill [repealing Obama's rule] because he believes in a conscience exemption in health care."

Likewise, he was kibitzing at a New Hampshire campaign event when he told a voter that he wants the minimum wage tied roughly to inflation. It was smart politics for a rich candidate who has been portrayed as failing to understand the poor. But when conservatives Rush Limbaugh and Larry Kudlow hammered him for "a policy that would make it more expensive to hire people," in the words of The Wall Street Journal's editorial page, he backpedaled. First he said he had vetoed a proposed minimum-wage hike as governor; then he said that inflation today "would tell you that right now there's probably not a need to raise the minimum wage."

If Romney wins the nomination, he'll have to appeal to the middle again, which could mean moderate views on immigration, war with Iran, taxes, or non-negotiation with the Taliban. (Would that make him a flip-flip-flopper?) The Obama campaign is already readying an ad blitz on this score that will make Bush's 2004 attacks on John Kerry look meek, according to officials familiar with the strategy who asked not to be named.

Yet even as Romney hopes to appeal to the center, the Republican voters in the process of nominating him will not let him off the hook. The GOP is no longer a party around which the rank and file dutifully rally. Already, conservatives parse his language tirelessly. Romney's profession that he is a "severe conservative" might have been an unnoticed solecism in any other candidate. But to Richard Viguerie, chairman of ConservativeHQ.com, it was another sign that "he can mouth the words conservatives use, but he has no gut-level emotional connection with the conservative movement and its ideas and policies."

So Romney, as the nominee, would have to fight a rearguard action while the Obama machine blitzes him frontally and centrists question his sincerity. His electoral results so far offer a glimpse at the problem. Take Ohio, a state that historically has been crucial to the success of any Republican candidate. Romney eked out a 1 percent plurality over Santorum only by taking the big urban and suburban centers -- Cleveland, Cincinnati, Columbus -- that traditionally vote Democratic. He lost most of the traditional Republican districts and 69 of Ohio's 88 counties. Even in relatively moderate Virginia, Romney's only opponent, Ron Paul, got 40 percent of the vote. Never mind what happened farther South and in the West, where (except for Idaho) the GOP base overwhelmingly rejects Romney.

But let's say that Romney pulls it off and wins the election. Whom do we end up with? Both Republicans and Democrats who have known Romney for years say that the candidate of 2012 is all but unrecognizable. "I don't know who he is or what he stands for," says one senior Republican adviser who is old enough to have known Romney's father and compares the son unfavorably. Gruber believes that Romney has already become someone else, perhaps a hybrid: "I don't think we're going to get the old Mitt Romney back," he says.