GOP Presidential Candidates
GOP Presidential Candidates REUTERS/Scott Audette

A fight is brewing in the U.S. South between Rick Santorum and Newt Gingrich, while Mitt Romney's priority is winning Arizona and Michigan as he keeps an eye on Ohio.

Those are the presidential campaign strategies becoming clear as fundraising efforts and spending plans shine some light on how the Republican race will play out through February and on to a showdown on Super Tuesday on March 6 when 10 states vote.

The next few weeks are the first notable lull since last year in the state-by-state contest for the Republican nomination to challenge Democratic President Barack Obama in November's election. Candidates are using it for a critical replenishment of funding.

Cash will be needed to campaign and advertise in the 10 Super Tuesday states that cover extensive territory and include the expensive state of Ohio, among the top 10 U.S. media markets.

Both Santorum and Gingrich are planning visits to California to raise money as they gear up for a fight over who is the conservative alternative to front-runner Romney.

Long trailing the pack in fundraising, Santorum has raised $3 million for his campaign since his surprise victories in three states' nominating contests on Tuesday. That is more than his campaign raised all of last year.

His allies at the Super PAC Red, White and Blue Fund plan to step up their game in Arizona as well as Super Tuesday states Ohio, Tennessee, and Georgia, where they will bankroll polling and phone banks to convince voters to back Santorum.

We are immediately going into states with voter-advocacy efforts and survey research where we had not originally planned, the PAC's adviser, Stuart Roy, said in an email. We are taking a hard look at states that may have previously been viewed as completely uphill.

Santorum, a former U.S. senator from Pennsylvania, will travel to the West Coast state of Washington early in the week and visit Michigan and Ohio in the Midwest later this month. His campaign also plans stops in the Southern states, but his schedule has not been settled.

The Southern Struggle

Gingrich, who represented Georgia for years in the U.S. House of Representatives, had been deemed a favorite in his home territory, but Santorum's strong emergence is turning up the heat.

Both [Gingrich] and Santorum assume that Mitt is not going to do well in Old Dixie, and they're both trying to compete there, said Republican strategist John Feehery.

Gingrich, who has been replaced by Santorum as the No. 2 contender in the Republican race, is planning visits this month to Oklahoma, Tennessee, and Georgia as well as Texas as part of his Southern strategy, although donor-rich Texas will not vote until at least April. The former House speaker campaigned in Ohio this week.

The Gingrich campaign has a new set of fundraisers and this week held a significant fundraising call with donors, Texas Gov. Rick Perry and his fundraisers, said Robert Walker, who chairs Gingrich's campaign. We think that we're in a very strong cash position and we think that we're capable of doing Super Tuesday and beyond, Walker said. We're budgeting to go all the way to the convention.

The struggle between Santorum and Gingrich could be a political fight to the death.

It's unlikely that both Santorum and Gingrich will survive past Super Tuesday, said Republican strategist Jack Burkman.

However, the pro-Gingrich Super PAC plans to keep its sights not on Santorum but on Romney as the main rival, said Rick Tyler, senior adviser to the group called Winning Our Future.

Gingrich is moving into a weak position, with Santorum surging, said Burkman. They are trying to show that the race is between him [Gingrich] and Romney ... I think it's smart.

Romney Must-Wins

After surprisingly heavy losses to Santorum in Missouri, Minnesota, and Colorado this week, Romney must win the two primaries before Super Tuesday -- in Arizona and Michigan -- to avoid the impression his campaign is going off the rails.

The determination to win in those two states is reflected in ad buys by the pro-Romney Super PAC Restore Our Future, which is already on air with an anti-Gingrich ad in Arizona and Michigan, where Romney's father was governor and Romney himself will travel later this month.

Looking toward Super Tuesday, the Super PAC is also running the ad in Ohio, where ballots can be cast early. The PAC hit Gingrich with a similar pummeling in Florida, dominating the early vote there.

Romney needs those states to get some mojo going, GOP strategist Feehery said. He's got to stop the momentum going the other way.

Romney is by far the best fundraiser of the four Republican candidates, although he still falls short of the campaign war chest being accrued by Obama.

In the past week, Romney held two fundraisers in Atlanta and Washington. They attracted dozens of guests who had raised at least $10,000. Several hundred people turned out. Tickets for the general public cost $1,000 -- or $2,500 for a chance to take a photo with the candidate.

Building on the experience of Romney's unsuccessful run for the Republican nomination in 2008, his national finance team is nearing completion and holds twice-weekly calls with fundraisers. Romney is expected to hold a fundraiser in Texas next week.

(Editing by Alistair Bell and Peter Cooney)