Eighteen days after the press pack wrote him off for the second time, Newt Gingrich surged to victory in the South Carolina primary on Saturday, halting the coronation of a suddenly stumbling Mitt Romney.

Buoyed by a pair of strong debate performances, withering attacks on the media and a plea for conservatives to unite behind a single champion, Gingrich won the late deciders 2 to 1 in scrambling the Republican race, instantly transforming himself into Romney’s chief rival.

With over 99 percent of the vote counted, Gingrich was beating Romney 40 to 28 percent, with Rick Santorum well back at 17 percent and Ron Paul at 13 percent.

Rick Santorum, the (belated) winner in Iowa, who had been battling Gingrich for that distinction, is the unambiguous loser. ABC, MSNBC and Fox News projected Gingrich the winner the moment the polls closed at 7 p.m., indicating a sizable margin.

The campaign now looks to be a long slog, with the next contest in 10 days in the mega-state of Florida, and Romney remains the best-organized and best-financed contender. But what Gingrich accomplished in South Carolina was nothing short of remarkable.

He managed to turn a blast from his tawdry past—an ABC interview with his second ex-wife, Marianne—into a crowd-pleasing ovation by attacking both the network and CNN (for asking about it) at Thursday’s debate in Charleston. Marianne Gingrich’s account that Newt had asked her to share him with his mistress (and current wife) Callista will undoubtedly hurt the former House speaker among female voters, but in the short run he portrayed himself as the victim of an unfair media assault.

Gingrich showed far greater skill in defusing that weakness than Romney did in addressing what has become his Achilles heel: the way he accumulated and manages his wealth. Backpedaling on whether to release his tax returns, letting drop that he pays a 15 percent rate, dismissing as chump change his $374,000 in speaking fees, the former Massachusetts governor looked hesitant and tone-deaf. And Gingrich managed to tone down his rhetoric about Romney’s former firm, Bain Capital, while still depicting Mitt as heartlessly squeezing struggling companies for huge profits.

Romney punched back in his concession speech without naming Gingrich, saying he has joined President Obama in an “assault on free enterprise,” as well as never having “run a business” or “run a state.”

Gingrich, for his part, cast himself as a truth-teller against a corrupt establishment. The American people, he intoned, feel that “elites” have been “trying for half a century to force us to quit being American.” He also took repeated shots at the “elite media” and the “growing anti-religious bigotry of our elites.”

On the gender front, there may have been a Marianne Effect: CNN exit polls showed Gingrich winning 41 percent of men in South Carolina men and 36 percent of women. But for all his baggage, dating to his tumultuous reign as speaker, Gingrich is a more adept and instinctive politician, while Romney is even-tempered and disciplined, except in unscripted moments. And he channeled conservative resentment toward Barack Obama and the liberal establishment in a full-throated way that Romney, with his management-consultant background, would never attempt. Gingrich got a last-minute boost when Rick Perry dropped out of the race and endorsed him.

He also, it should be noted, played a bit of racial politics, denigrating Obama as the “food stamp president” and chiding Juan Williams in the Fox debate for suggesting that his comments were demeaning toward blacks. And there appears to be a strong evangelical undercurrent: Among those in exit polls who said religion matters a great deal to them, Gingrich beat Romney 43 to 9 percent. Some Christian conservatives may have been reluctant to back a Mormon candidate.

Still, Gingrich was up against South Carolina’s history of shoring up established candidates against insurgents, and the constant specter of Gov. Nikki Haley stumping with Romney.

Gingrich seems to run better from behind. Ever since most of his staff quit last summer—the first time the press wrote his political obituary—Gingrich has prided himself on being his own political strategist. His skills seemed to fail him last month when he lost a big lead in the Iowa caucuses, stubbornly staying positive (most of the time) while a pro-Romney super PAC hit him with more than $3 million in negative ads. The pundits declared him toast again, saying he was staying in the race just to wound Romney.

But Gingrich mapped a more aggressive path in South Carolina, boosted by a pro-Newt super PAC, which ran anti-Romney ads backed by $5 million from Las Vegas casino mogul Sheldon Adelson.

Before the hyperventilating press gets carried away in the other direction and starts speculating on a Newt-vs.-Obama race, it’s worth recalling that a grand total of three states have now voted. Still, with Romney’s aura of inevitability shattered, he is facing his toughest test since announcing his second bid for the White House. If he makes the necessary adjustments, he’ll be a stronger nominee. If he doesn’t, we are in for a long battle until the convention.