It's Iowa minus one month, and barring yet another resurrection, or something of similar improbability, it's Mitt Romney vs. Newt Gingrich. In a match race, here's the scorecard:

Romney has managed to weather the debates unscathed. However, the brittleness he showed when confronted with the kind of informed follow-up questions that Bret Baier tossed his way Tuesday on Fox's "Special Report" – the kind of scrutiny one doesn't get in multiplayer debates – suggests that Romney may become increasingly vulnerable as the field narrows.

Moreover, Romney has profited from the temporary rise and spontaneous combustion of Michele Bachmann, Rick Perry and Herman Cain. It required no exertion on Romney's part.

Enter Gingrich, the current vessel for anti-Romney forces – and likely the final one. Gingrich's obvious weakness is a history of flip-flops, zigzags and mind changes even more extensive than Romney's – on climate change, the health care mandate, cap-and-trade, Libya, the Ryan Medicare plan, etc.

The list is long. But what distinguishes Gingrich from Romney – and mitigates these heresies in the eyes of conservatives – is that he authored a historic conservative triumph: the 1994 Republican takeover of the House after 40 years of Democratic control.

Which means that Gingrich's apostasies are seen as deviations from his conservative core – while Romney's flip-flops are seen as deviations from … nothing. Romney has no signature achievement, legislation or manifesto that identifies him as a core conservative.

So what is he? A center-right, classic Northeastern Republican who, over time, has adopted a specific, quite bold, thoroughly conservative platform. His entitlement reform, for example, is more courageous than that of any candidate, including Barack Obama. Nevertheless, the party base, ostentatiously pursuing serial suitors-of-the-month, considers him ideologically unreliable. Hence the current ardor for Gingrich.

Gingrich has his own vulnerabilities. The first is often overlooked because it is characterological rather than ideological: his own unreliability. Gingrich has a self-regard so immense that it rivals Obama's – but, unlike Obama's, is untamed by self-discipline.

Take that ad Gingrich did with Nancy Pelosi on global warming advocating urgent government action. He laughs it off today with "that is probably the dumbest single thing I've done in recent years. It is inexplicable."

This will not do. He was obviously thinking something. What was it? Thinking of himself as a grand world-historical figure, attuned to the latest intellectual trend (preferably one with a tinge of futurism and science, like global warming), demonstrating his own incomparable depth and farsightedness. Made even more profound and fundamental – his favorite adjectives – if done in collaboration with a Nancy Pelosi, Patrick Kennedy or even Al Sharpton, offering yet more evidence of transcendent, trans-partisan uniqueness.

Two ideologically problematic finalists: One is a man of center-right temperament who has of late adopted a conservative agenda. The other, more conservative by nature, is possessed of an unbounded need for grand display that has already led him to unconservative places even he is at a loss to explain, and that as president would leave him in constant search of the out-of-box experience – the confoundedly brilliant Nixon-to-China flipperoo regarding his fancy of the day, be it health care, taxes, energy, foreign policy, whatever.

The second, more obvious, Gingrich vulnerability is electability. Given his considerable service to the movement, many conservatives seem quite prepared to overlook his baggage, ideological and otherwise. This is understandable. But the independents and disaffected Democrats upon whom the general election will hinge will not be so forgiving.

They will find it harder to overlook the fact that the man who denounces Freddie Mac to the point of suggesting that those in Congress who aided and abetted it be imprisoned, took $30,000 a month from that very same parasitic federal creation. Nor will independents be so willing to believe that more than $1.5 million was paid for Gingrich's advice as "a historian" rather than for services as an influence peddler.

My own view is that Republicans would have been better served by the candidacies of Mitch Daniels, Paul Ryan or Chris Christie. Unfortunately, none is running. You play the hand you're dealt. This is a weak Republican field with two significantly flawed front-runners contesting an immensely important election. If Obama wins, he will take the country to a place from which it will not be able to return (which is precisely his own objective for a second term).

Every conservative has thus to ask himself two questions: Who is more likely to prevent that second term? And who, if elected, is less likely to unpleasantly surprise?

© Copyright The Sacramento Bee. All rights reserved.

Charles Krauthammer is distributed by the Washington Post Writers Group.

• Read more articles by Charles Krauthammer