Michael Barone‘s latest column explains how South Carolina’s history of choosing the eventual Republican presidential nominee helps frontrunner Mitt Romney.

He got louder cheers than Santorum or Paul, and Gingrich got boos when he attacked Romney at the Faith and Freedom tent and at the debate. Romney has been leading in South Carolina polls this month, with Gingrich gaining only slightly and Santorum surging after Iowa and then falling back a bit after New Hampshire.

Both Santorum and Gingrich depict themselves as bold conservative alternatives to Romney. Santorum says he’s stronger because he beat Gingrich in Iowa and New Hampshire.

Gingrich says he is because he’s polling better in South Carolina, where most voters remember his stint as speaker of the House and where Santorum has not done the intensive campaigning that impressed Iowans.

But neither has found a wedge issue that undermines the frontrunner. In Monday’s debate Gingrich edged away from his attacks on Romney’s business record. Santorum took the alpha-male role over Romney in one heated interchange, but in support of a proposal — voting rights for released felons — not popular with South Carolina Republicans.