WASHINGTON - A resurgent Rick Santorum hopes to spring his next big surprise in Michigan. Newt Gingrich looks for a campaign revival in the Bible Belt. Mitt Romney has his home state of Massachusetts, and the luxury of picking his spots elsewhere, if not everywhere, as the race for the Republican presidential nomination roars back to life.

After a brief midwinter lull, the Republican field faces a cross-country series of nine primaries and four caucuses between Feb. 28 and Super Tuesday on March 6. At stake are 518 delegates, more than three times the number awarded so far in the unpredictable competition to pick a GOP opponent for President Barack Obama.

A debate on Feb. 22 in Arizona, the first in three weeks and possibly the last of the GOP campaign, adds to the uncertainty.

The political considerations are daunting as Romney, Santorum, Gingrich and Ron Paul weigh the cost of competing in one state against the hope of winning in a second or perhaps merely running well but gaining delegates in a third.

"Not all states are of equal importance," said Steve Schmidt, who helped the GOP's 2008 nominee, Arizona Sen. John McCain, navigate the campaign calendar as a senior adviser.

According to numerous strategists inside and outside the campaigns, the Michigan primary on Feb. 28 shapes up as particularly important contest as Romney tries to fend off a charging Santorum one week before a 10-state night on Super Tuesday.

Yet of the 13 states, Georgia has the biggest delegate haul at stake, 76, and Gingrich can ill afford to lose now where his political career was launched in 1978.

Sensing an opportunity, the pro-Romney group Restore Our Future is targeting Gingrich in television ads in the state, hoping to deny the former House speaker a sweep of the delegates and leave some on the table for Romney to scoop up.

Not such maneuver is possible in Arizona. There, all 29 delegates go to the winner, and Romney, a former Massachusetts governor, is heavily favored.

"If you're the front-runner, and inevitability or electability are things that are driving the ballot, it's important to do a combination of both" win states and accumulate delegates, Schmidt said in an interview, offering a description of the situation that Romney confronts.

For Romney's rivals, first-place finishes are critical to creating or maintaining the impression of momentum, said Terry Nelson, who was a top strategist for campaign dropout Tim Pawlenty, a former Minnesota governor.

"It's going to matter more for Rick Santorum and Newt Gingrich because their campaigns are more reliant on cash flows and they need the victories to maintain that," he said.

All candidates share one objective, he added. "You go from win to win."

Texas Rep. Ron Paul, the only of the four contenders without a victory so far, eyes four chances to break through: caucuses in Washington on March 3, and in North Dakota, Idaho and Alaska three days later. An unusual presidential campaign trip to Alaska is possible.

Nor are the candidates the only ones working to shape the race.

Restore Our Future, the political organization that supports Romney and has devastated Gingrich with attack ads in two states, is turning its attention to Santorum, a former Pennsylvania senator.

Already, the group has spent $5 million on television advertisements combined in Arizona and Michigan through Feb. 28, and Ohio, Tennessee, Oklahoma and Georgia through Super Tuesday. The group also has commercials airing in Mississippi and Alabama.

Santorum responded with a commercial in Michigan designed to blunt the attacks and tarnish Romney. It shows a Romney lookalike wielding a machine gun that sprays mud in Santorum's direction.

When the weapon jams, the gunman tries to fix it, and ends up splattering himself instead.

The Red White and Blue Fund, which supports Santorum, is advertising in Michigan, but the former senator and his allied group are being outspent roughly 3-1 by Romney and Restore Our Future.

"We know that we're going to win some and were going to lose some, but we have the resources and the organization to go the distance even if that means a primary calendar that extends into the spring," said Gail Gitcho, communications director for Romney.

With Gingrich unable to come close to duplicating his Jan. 21 victory in South Carolina, his goals are as diminished as his campaign bank account.

"We want to aim at Washington state with 40 delegates. We want to do as best as we can in Michigan, but understanding there's a larger strategic gain for us if a consensus builds around the idea that Mitt Romney is unacceptable as the nominee," campaign spokesman R.C. Hammond said.

He said Ohio, Georgia, Oklahoma and Tennessee are priorities.