There is a possible scenario under which Mitt Romney could lose the Republican presidential nomination.

Rick Perry, Herman Cain or Michele Bachmann galvanize social-issue conservatives and might win the Iowa caucuses in early January. A week later, the often contrarian and independent-minded primary voters in New Hampshire could upset the odds and vote for Cain, or more probably, Jon Huntsman.

Most likely, though, Romney will win at least one of these crucial contests and become the unstoppable front-runner.

That is why, not surprisingly, both the more establishment centrist Republicans and the populist, movement conservatives are now focused on figuring out exactly who is the real Romney. Surprisingly, they pretty much agree: He’s a contemporary version of President George H.W. Bush, the 41st president, slightly to the right of the political center, more inclined to favor reasonable limits on the role of government than to want to dismantle it, and preferring consensus to confrontation.

For the centrists, this definition of the potential nominee brings hope; for conservatives, it breeds fear.

Everyone agrees he’s exceptionally intelligent; one Democratic political operative who was a consultant to Romney on the health-care measure he put in place as governor of Massachusetts says he has never worked with a smarter politician on policy. His personal integrity is exemplary.

Abortion Stance

Yet when it comes to policy, there are few national figures who have so dramatically changed positions: Romney has gone from a strong defender of reproductive rights to a foe of all abortions, and from claiming to be a stronger advocate for gay rights than his 1994 Senate opponent, the liberal Edward M. Kennedy, to his current support for a constitutional amendment banning same-sex marriage.

The stakes, however, are much larger when it comes to the economy. This was on display last week during the Bloomberg- News/Washington Post candidate debate that focused on that topic.

Take the issue of the government’s role in the 2008 financial crisis — and particularly the Troubled Asset Relief Program — which splits Republicans. The establishment types believe the bank rescue saved the global financial system from collapse, while more grassroots Republicans see it as an unconscionable bailout of financial institutions deemed too big to fail.

Financial Bailout

In his book, “No Apology,” Romney lends support to both views. “It doesn’t make sense to bail out individual companies or banks or financial institutions that get in trouble,” he writes. “Creative destruction is part of a growing, productive economy.”

He also says the Republican administration’s rescue efforts in 2008 weren’t aimed at saving banks but at averting a “total meltdown” of the economy. Later, he suggests that TARP under Treasury Secretary Henry Paulson was good, while under his Obama administration successor, Timothy Geithner, the same program was bad.

When asked at the debate what he would do, as president, in a similar situation, Romney tried to duck; ultimately, he acknowledged that he probably would do the same thing.

He offers similar contortions on budgetary matters. During the debate, and in his 59-point economic program, Romney vows to oppose any tax increases and says deficit reduction should be accomplished only through spending cuts.

Balanced Budget

He’s vague about the specific cuts to Social Security or Medicare he would undertake, even as he calls for a balanced- budget amendment to the Constitution, which would make such cuts inevitable. (One of Romney’s judicial advisers, the conservative Judge Robert Bork, has warned that a balanced-budget requirement would open the door “to hundreds, if not thousands of lawsuits around the country,” leaving decisions about what to cut in the hands of unelected judges.)

The Republican front-runner’s fiscal challenges are compounded by his appeals to hard-line hawks within the party. He would increase defense spending about $50 billion a year over President Barack Obama’s request, add Navy vessels, revive the missile-defense system and increase force levels by 100,000; it’s not clear what he would do with the extra troops as the U.S. is drawing down forces in Iraq and Afghanistan.

When asked to make recommendations to the congressional supercommittee that’s supposed to devise a deficit-reduction plan in the next five weeks or trigger across-the-board spending reductions, including in defense, Romney reiterates his mantra of no additional revenue, no defense cutbacks, and no automatic cuts.

That keeps him out of the crosshairs of populist conservatives.

‘Grand Bargain’

If he were to be confronted by the same partisan divide as president, look again to the Bush 41 model, some of those who know Romney well predict; that would mean some effort at a “grand bargain” deficit-reduction package.

On immigration, Romney has taken a much tougher posture in recent years. Similarly, this long-time advocate of free trade now vows to label China a currency manipulator and impose tariffs on its goods.

Establishment Republicans say that’s just campaign rhetoric aimed at playing to public opinion. The populist conservatives, many of whom are anti-immigrant and anti-China, worry they’re right.

Health Care

Such contradictions pervade his defense of his health measure in Massachusetts. He is right in claiming that it improved care in the Commonwealth.

It also, with its mandate requiring everyone to buy health insurance, was a model for Obama’s 2010 measure, which rank-and- file Republicans despise. Jonathan Gruber, a health-care expert from the Massachusetts Institute of Technology, who consulted with both Romney and Obama, calls the ex-governor “the intellectual father of national health reform.”

To date, thanks to the ineptitude of his primary opponents, Romney has largely avoided unfair critiques of his signature measure. In a general election, that’s not a charge Obama can make.

A glance at Romney’s political standing underscores this conundrum. He runs even with Obama in hypothetical general- election matchups, a good spot for a challenger at this stage. Few question his competency to be president.

In the Republican contest, however, Romney remains mired in polls with about a quarter of the vote, while the flavors du jour — Bachmann two months ago, Perry last month, and now Cain — rise and fall. Most Republican voters prefer an alternative.

As the last candidate standing, Romney is likely to overcome these doubts and then would be an even bet to win the White House next autumn. If he reaches the Oval Office, he’ll bring these conflicts with him.

(Albert R. Hunt is the executive editor for Washington at Bloomberg News. The opinions expressed are his own.)

To contact the writer of this column: Albert Hunt in Washington at ahunt1@bloomberg.net

To contact the editor responsible for this story: Max Berley at mberley@bloomberg.net.