The New Hampshire primary is next on the Republican presidential calendar – Jan. 10. But the South Carolina primary, which follows New Hampshire on Jan. 21, will likely be much more important, Politico reports.

Former Massachusetts Gov. Mitt Romney has a huge lead in polls for New Hampshire, a moderate state, so unless he surprisingly falters in the next five days, the result means very little. His main conservative competitors, former Pennsylvania Sen. Rick Santorum and former House Speaker Newt Gingrich, aren’t seen as viable threats in New Hampshire.

While they’re not giving up in New Hampshire, both are counting a lot more on South Carolina. And Texas Gov. Rick Perry has given up on New Hampshire. For him it’s South Carolina or bust.

Many Republicans see South Carolina as perhaps their last chance to keep Romney from seizing the nomination.

“South Carolina will become the ground on which an ‘ABM’ movement starts to coalesce — the anybody-but-Mitt crowd,” veteran South Carolina GOP strategist Tucker Eskew told Politico. “Perhaps not successfully, but there will be a drive to coalesce that vote.”

Even prominent New Hampshire conservative Charlie Arlinghaus, head of the conservative Josiah Bartlett Center for Public Policy, says South Carolina is the key primary for the conservative candidates.

“If you can’t have a breakout moment in one of the first three states, you’re in trouble, and, for all of the conservatives, South Carolina is the most fertile ground,” he told Politico. “New Hampshire has been quieter this year than it’s been in the past because Romney has been so dominant here.”

The conservative candidates certainly have been giving the Palmetto State a lot of attention.

Even before Tuesday’s Iowa caucuses, Gingrich indicated South Carolina is his Ground Zero. “The gap between Romney’s moderate Massachusetts views and Southern conservatism is, oh, about the distance from Boston to Charleston,” he said at a campaign stop.

Santorum has said for weeks that he wants a strong showing in Iowa, a better-than-expected finish in New Hampshire, and then a rousing victory in South Carolina to send him on his way to the nomination.

As for Perry, without a win or a strong second-place finish in South Carolina, his campaign is probably toast. Even before the Iowa caucuses, Perry made time to put the spotlight on the Palmetto State, telling  CNN,  “A Massachusetts governor that put individual mandates in place that Obama took as the model to create Obamacare is not going to sell in South Carolina.”

The calculus of the state’s primary isn’t simple. While its Republicans certainly skew more conservative than New Hampshire’s, it’s also home to many wealthy Republicans focused on the economy and military veterans who won’t necessarily vote on the basis of ideology. Moderate John McCain took the South Carolina primary in 2008.

Romney may gain a big benefit from Perry’s decision to stay in the race – he had indicated to some supporters that he would withdraw after his poor showing in Iowa. Now Romney can hope a split among conservative voters between Santorum, Gingrich and Perry will enable him to emerge victorious.

To be sure, Romney will likely have to do a lot better than his 15 percent total in the 2008 South Carolina primary to top the field this time around.

A Winthrop University poll taken in early December showed Romney losing the state by 17 percentage points to Gingrich. While the former House speaker’s campaign has taken a downturn since then, Southern voters in Gallup’s national GOP primary polling have consistently been the most enthusiastic about anti-Romney conservatives, from Perry to Gingrich.

“I think the traditional religious social conservatives will be very important in South Carolina, and they will decide who wins down here,” Rich Bolen, Lexington County GOP chairman, told Politico. “I think Mitt Romney’s support for his healthcare ideas in Massachusetts will not play well here. And even though people won’t say it, his Mormonism won’t play well here.”

The state’s importance isn’t lost on Romney. Instead of putting all his focus on New Hampshire this week, he has scheduled several appearances in South Carolina. And the Romney campaign already has launched television ads there.