Newt Gingrich's victory in South Carolina didn't simply expose the weakness of Mitt Romney but also that of the GOP establishment. For several decades, the establishment and movement conservatives have coexisted. But all along, the Right has sought to extinguish the influence of establishment moderates. Now it may be on the verge of accomplishing this decades-long goal, one that began with the Goldwater run for the presidency in 1964, continued with the election of Ronald Reagan and, two decades later, with George W. Bush.

Gingrich's victory has elicited much concern among those Republicans who see him as a volatile and unpredictable force. They are correct. Gingrich's volatility and unpredictability have been evident for several decades. But they are also the very qualities that propelled him to the House speakership in 1994. He is a guerrilla insurgent, a Republican Maoist who seeks to topple the old order. In an era where the ancien régime is looking fragile, Gingrich is most representative of the populist anger that many Americans feel toward Wall Street and the political establishment, both of which Mitt Romney, no matter how much he disclaims it, represents.

There is no small dose of hypocrisy in Gingrich's pious asseverations about Romney's record as a capitalist fiend. Gingrich, who claims he has not been a lobbyist but merely a historian advising Freddie Mac for $1.7 million during his recent years in Washington, appears to have belatedly discovered a social conscience. But Romney's problem remains himself. For one thing, the credentials of a former Paul Tsongas supporter are inevitably going to be suspect to conservatives. Romney has undergone the presidential equivalent of confirmation conversion, blithely jettisoning positions on healthcare and global warming and abortion that he once enthusiastically endorsed. His perceived inauthenticity may be deadly in at a moment when the public is smarting over the shenanigans of political and financial leaders. Gingrich nailed Romney's conundrum on Face the Nation, saying "he's been dancing on eggs trying figure out how to find out a version of Romney that will work."

Gingrich, by contrast, can pose as someone who has been to the abyss and is now seeking redemption. It's a narrative that any Hollywood producer would understand. He may have checked his principles at the door in the past, but now he's come back home to save the family ranch from the local bank president who wants to confiscate it. In essence, conservatives, you might say, fear that Romney will do to the GOP what he did with Bain—act like a takeover artist who guts the innards of an enterprise, marks it down and walks away with a smile. Romney, in other words, might compromise as president in order to boost his own popularity. A Romney presidency, they fear, would leave a shell of a GOP at the very moment that it seems about to return to the old-time doctrines of conservatism that were watered down for decades by moderates such as Gerald Ford and George H.W. Bush. As Liz Cheney told the New York Times, "He demonstrated the kind of fighting spirit that people out there who are really worried about a second term for Barack Obama really want to see."

What would a Gingrich nomination actually look like? In foreign policy, he would be pure neocon. In domestic policy, he would push hard for further tax cuts. But throughout, his unbridled nature would probably terrify the broad mass of voters. Unless Gingrich was able to reinvent himself again, he could lead the GOP to an electoral disaster not only in the presidency race but also in Congress.