In Michigan last week and in Ohio last night, Mitt Romney came within a few points of suffering defeats that the political world would have regarded as catastrophic. In both states, his margin of victory over Rick Santorum was smaller than the share of the vote won by a third candidate, Newt Gingrich. In Ohio, Gingrich's effect was particularly pronounced: Romney won the state by one point, or about 12,500 votes, and the former speaker took 15 percent, or about 175,000 votes.

As narrow as they were, the Michigan and Ohio outcomes had serious psychological value for Romney. The Michigan vote was the culmination of what amounted to a weeks-long viability test him; losing by even one vote would have plunged his campaign into crisis, sent key Republican opinion-shapers into a panic, and raised the possibility of Santorum actually winning the nomination. In victory, Romney managed to calm the waters, but a surprise loss in Ohio last night would brought all the turmoil back. As it was, Super Tuesday was an unexpectedly shaky night for him, but it could have been far worse.

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Is Gingrich the reason Romney averted disaster last night? It's impossible to say for sure, but a strong case can be built. In Ohio, Gingrich's support was more spread out demographically and ideologically than Santorum's, but he performed particularly well with certain groups that otherwise seemed to prefer Santorum. For instance, nearly a third of the GOP electorate identified as strong Tea Party backers. Santorum beat Romney by nine points (41 to 32 percent) among them, but Gingrich also won 20 percent of them. Santorum needed to run up as big a margin as possible with this group, since he lost to Romney among those who "somewhat" support the Tea Party, have no opinion on it, or are opposed to it, and Gingrich clearly got in his way.

Gingrich also stole a state, Georgia, that almost certainly would have gone for Santorum otherwise. The basic demographic profile of Georgia's electorate, 39 percent "very conservative" and 64 percent evangelical, was a bad match for Romney, who is struggling (as he did in 2008) mightily in the South and areas that are culturally southern. But because Gingrich ran as a favorite son, the anti-Romney conservative vote -- and a bundle of delegates -- went to him in the Peach State. Plus, while Santorum netted positive headlines from his wins in Tennessee and Oklahoma, Gingrich's strength in both states (24 percent of the vote and 28 percent, respectively) denied Santorum more impressive-seeming margins and extra delegates.

This is probably the outcome that Sheldon Adelson had in mind when he cut his most recent $10 million check to the pro-Newt super PAC. The Las Vegas casino magnate, a longtime Gingrich benefactor who was drawn to Republican politics mainly because of Israel and Middle East issues, has made it clear that he known Gingrich's campaign is doomed, that he doesn't care for Santorum's cultural conservatism, and that he's eager to help Romney unseat Barack Obama in the fall. His most recent super PAC donation came with the expectation that it wouldn't be used to attack Romney. The calculation was transparent: A viable Gingrich make it much harder for Santorum to corner the market on the most conservative and religious voters in the Republican Party, allowing Romney to .... well, to have the kind of night he had last night.

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Santorum's campaign will apparently step up its efforts to convince Gingrich to leave the race now. Good luck with that. It's true that Gingrich actually had a pretty awful night last night, but he doesn't seem to recognize it. In a way, he's been playing with house money since last fall, when he first surged in polls -- something that was never supposed to happen after his epically humiliating spring and summer. Now he's won two big southern states and controls more than 100 convention delegates. And Santorum is going to tell him to fold his tent -- especially when two more southern states, Mississippi and Alabama, are on next week's docket?

It's probably too late for Santorum to win the primary season delegate race. NBC is estimating that Santorum would need to win more than 60 percent of the remaining delegates to reach the magic 1,144 mark -- and nearly 70 percent if you assume Romney will win the remaining contests in New England and the Northeast. But there's still enough conservative and evangelical resistance to Romney for Santorum to make some serious trouble. He barely missed a chance for a breakthrough last night, just like he did in Michigan a week ago, and as long as Gingrich is around, this is the fate Santorum is doomed to keep living out. It's almost like someone planned it this way.