A notion ridiculed a few short weeks ago is now becoming more plausible -- even if it's not yet a likely outcome.

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Library of Congress

Is it time to take the Republican convention seriously as a potential battleground?

Republicans should know better by now. Their still-putative nominee, Mitt Romney, lacks the conservative support to capture the kind of expectations-exceeding primary win necessary to capsize underfunded but motivated rivals Rick Santorum and Newt Gingrich.

Romney didn't do it in South Carolina, Colorado, or Tennessee. He proved unable once again Tuesday to claim victory in a state, Mississippi, that seemed tantalizingly within reach.

The months-long trend makes clear Romney will have to win the GOP nomination with math, not acclamation, steadily accumulating enough delegates in friendly contests until he reaches the nomination-clinching number of 1,144. But that path is fraught with risk. There is always the chance that he'll fall just short of the magic number, which raises the possibility of a contested convention this August in Tampa.

The notion was mocked by many a month ago but now seems increasingly likely. "After last night, you have to start think it's possible,'" said Republican political consultant Curt Anderson, a former political director of the Republican National Committee who advised Rick Perry before he quit the race. "It seems more possible than before, that's for sure." The Santorum and Gingrich campaigns are each eagerly embracing that very scenario.

In a memo released this week, the Santorum campaign argued that some delegates ostensibly pledged to Romney would switch to the onetime U.S. senator if Romney fails to win on the first ballot at the convention. Combined with a difficult remaining schedule for Romney, that dynamic ensures Romney won't acquire enough delegates, the Santorum campaign contends.

"The reality is simple: The Romney math doesn't add up, and he will have a very difficult time ever getting to a majority of the delegates," the memo said. "The situation is only going to get worse for them and better for Rick Santorum as time passes. Simply put, time is on our side."

That sentiment was echoed by Gingrich supporters, including Rick Tyler, an official with the Gingrich-allied super PAC Winning Our Future. "We're in a position now where convention delegates are going to decide who nominee is," Tyler told National Journal.

Whether Gingrich will be at the convention seems like more of an open question, even as the candidate himself vowed Tuesday night to make his case all the way to Tampa. "Because this is proportional representation, we're going to leave Alabama and Mississippi with a substantial number of delegates, increasing our total going towards Tampa," he said. "We're going to take a much bigger delegation than we had yesterday."

The former House speaker's political base was supposed to reside in the Deep South, but the twin disappointments of Alabama and Mississippi will increase calls from some conservatives for him to step aside to let Santorum battle Romney one-on-one.

Gingrich's viability could depend on his super PAC, which, with the benefit of multimillion dollar donations from casino magnate Sheldon Adelson, has kept him visible on TV and radio. Whether those funds will continue to flow to and from the outside group remains unclear -- Tyler declined to comment. He did concede, however, that Gingrich had missed a chance Tuesday to "change the narrative." He added, "That doesn't mean it won't change tomorrow."

Tyler said Santorum, whose campaign has urged Gingrich to quit the race, actually would benefit from Gingrich sticking with it -- that way, the two men can work together to gobble up enough delegates to prevent Romney from reaching 1,144 of them. As Gingrich put it Tuesday night, "the conservative candidates" (meaning himself and Santorum) "got nearly 70 percent of the vote" in Alabama and Mississippi.

The Romney campaign pointed out that despite the disappointing returns in the South, it still increased its delegate lead thanks to victories in Hawaii and American Samoa. The Associated Press delegate count Wednesday put Romney at 495. Santorum had 252 and Gingrich had 131 -- well behind Romney even when added together.

"Our goal was to come in, take a third of the delegates," Romney senior adviser Eric Fehrnstrom said in an interview with CNN. "We'll do that, and once the dust clears, you'll be able to look and see that there really will be no ground that our opponents have made up against Mitt Romney, and as you look at the upcoming contest on the calendar, there are no opportunities for them to have significant wins that allow them to accumulate large numbers of delegates so they can close the gap with Mitt Romney."

It may not be inspirational, and it may not prevent drama at the convention, but it's a plan.

Beth Reinhard contributed.

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