But if the Rasmussen numbers hold, the campaign teams at Gingrich and Santorum headquarters are facing a potential knockout blow. Romney has a commanding delegate lead, and his rivals are both counting on the support of the deeply conservative, blue-collar voters that dominate Deep South primaries. If Romney demonstrates that he is able to curry favor with those voters, he will have a compelling argument for his competitors to clear the field.

Gingrich's campaign manager admitted as much in comments to reporters earlier this week, agreeing the states were "must wins." While the candidate backed off those comments somewhat — telling supporters on a conference call Thursday night he planned to go on to the convention regardless of the results — Gingrich's viability nevertheless rests on a Deep South strategy.

Romney is in the midst of a two-day swing through the state, visiting a Mississippi farmer's market Friday morning with Gov. Phil Bryant, who has endorsed his candidacy.