Now that the Republican presidential field has been effectively whittled to two, each of the front-runners has laid out a detailed plan to beat the other.

This much is clear: Whoever wins is going to win ugly.

Mitt Romney’s strategy calls for a slow, state-by-state accumulation of delegates to the Republican National Convention. In that process, he might not win the kind of enthusiasm that usually builds behind the party’s nominee.

But the former Massachusetts governor would win the numbers game, gaining the 1,144 delegates needed for the nomination sometime before July.

Romney’s chief rival, former senator Rick Santorum (Pa.) has outlined his own, more unlikely strategy: He might not be able to reach that key delegate threshold, his aides said, but he hopes to keep the party so split that Romney can’t hit it, either.

In that scenario, the race would remain undecided until the GOP’s convention in August. Then — in the first brokered convention in 60 years — Santorum could win over individual delegates and snatch the nomination.

“The reality is simple: the Romney math doesn’t add up and he will have a very difficult time ever getting to a majority of the delegates,” Santorum’s campaign wrote in a memo to supporters, dated March 10. “The situation is only going to get worse for them and better for Rick Santorum as time passes. Simply put, time is on our side.”

So far, 26 states and four territories have voted in this Republican primary season. There are 26 contests to go, including in Puerto Rico and the District.

A few things have actually been settled. For one, it’s clear that Santorum has found a way to win on the cheap. For each delegate he has earned, his campaign and a pro-Santorum super PAC have spent about $17,500 on TV ads, according to data from the Campaign Media Analysis Group. For Romney, the equivalent figure is about $67,700.

It’s also become clear that Romney has the money to win expensively. He has accumulated 495 delegates, nearly double Santorum’s total of 252.

Even on Tuesday, when Santorum won primaries in Mississippi and Alabama, Romney finished the night with more new delegates. He got a share of the delegates in each Southern state and gained even more with wins in Hawaii and American Samoa.

Finally, after Tuesday it became clear that former House speaker Newt Gingrich (Ga.) is no longer a serious contender for the nomination. After losing on his Southern home turf, he is too far behind, with too few friendly states left to vote. Still, he has shown no intention of formally dropping out.

‘This is a process’

On Wednesday, Romney acknowledged that he has had trouble attracting conservative voters. But, he said, when he wins that crucial 1,144th delegate, that problem will take care of itself.

“Last night, I got more delegates than anybody else. This is a process of becoming the nominee. We’re pursuing that in an intelligent way,” Romney said in an interview on Fox News Channel. “Some who are very conservative may not be yet in my camp, but they will be when I become the nominee when I face Barack Obama.”

In a memo released Wednesday, Romney’s aides reiterated what has become the central argument of his campaign: The math says nobody else can win.

“Santorum and Gingrich now trail Governor Romney by margins they cannot mathematically make up,” Romney adviser Rich Beeson wrote in a memo to reporters. “Senator Santorum is 255 delegates behind Governor Romney and Speaker Gingrich is 373 delegates behind. In order to win, both Santorum and Gingrich need to start netting an impossible number of delegates to overtake Governor Romney.”

By that logic, Romney will reach the required number of delegates no later than June 26, when Utah holds the last contest.

That would be an uncomfortable way to win. A long series of primary fights would drain Romney’s campaign treasury and could tarnish his image before a general election against Obama.

Already, Romney’s donors have grumbled that he doesn’t seem to be getting better as a campaigner.

“He just doesn’t connect. He doesn’t draw energy from his crowds,” one of Romney’s donors said Wednesday. The donor spoke on the condition of anonymity to talk about private discussions within the campaign.

“Both Newt and Rick are passionate in that sense, whether you agree with what’s coming out of their mouths or not,” the donor said. “They say it with passion and conviction. And you are who you are — and that’s just not in Mitt Romney’s DNA.”

A convention fight

In Santorum’s strategy, Utah is not the end. In the scenario sketched out by his advisers, after that primary Romney would be ahead, but not with enough delegates to clinch the nomination.

So the GOP convention would begin without a winner.

At that point, Santorum would try to woo delegates who had supported Gingrich, as well as others who came to the convention unpledged to any candidate. With their help, he could pass Romney and win in later rounds of balloting.

No major party has tried such a thing since 1952. They much prefer their conventions to be pep rallies instead of brawls.

Still, experts said, this ugly kind of win is the only hope for Santorum.

“There’s hardly any logic there. But that’s the only play they have right now,” said Josh Putnam, a professor at Davidson College in North Carolina who studies the Republican primary process.

Staff writer Nia-Malika Henderson contributed to this report.