Rick Santorum visits the governor's mansion in Old San Juan, Puerto… (Christopher Gregory, Getty…)
Reporting from Rosemont, Ill. — After a pair of pivotal Southern tests, the Republican presidential race has become a battle between Mitt Romney's grind-it-out delegate arithmetic and Rick Santorum's popular momentum.
It's not exactly an even nomination fight at the moment. Romney remains the clear favorite, though his campaign advisors don't expect him to lock up the needed 1,144 delegates before May, at the earliest. Santorum scored upset wins Tuesday in Mississippi and Alabama but is unlikely to gain enough delegates during the primary season to overtake Romney. Instead, the insurgent challenger is attempting to keep the front-runner from obtaining a majority before this summer's national convention.
That has added unexpected drama to next week's Illinois primary. "Santorum needs a big unexpected win to fundamentally alter the race," said Republican strategist Mike DuHaime, who is unaligned this year. Illinois, he added, would fit that category.
The state, large and diverse, is not as conservative as others where Santorum has been successful. But a recent Chicago Tribune/WGN poll showed him only 4 percentage points behind Romney statewide, with Newt Gingrich far back.
The Romney forces are again bringing their considerable financial muscle to bear, throwing millions of dollars into Illinois attack ads against Santorum, who has been slow to get on the air. The former Pennsylvania senator still lacks the financial resources to muster an effective ad response and is relying, as he has up to now, on support from social and religious conservatives and a hoped-for infusion of enthusiasm from his latest electoral successes.
"Santorum has to win on Romney turf. Period," Josh Putnam, a Davidson College political scientist who specializes in GOP delegate rules, said in an email. "He has to demonstrate that he can expand beyond the prairie (and surrounding) states and can branch out more than to just Gingrich territory. Otherwise, it won't be enough. Illinois would be a good starting place."
Romney's "best opportunity" involves a win in Illinois, victories in Maryland, Washington, D.C., and Wisconsin on April 3, and a stellar showing in the five mid-Atlantic/Northeastern states on April 24, he said.
The fastest route for Romney to gain the delegates needed to secure the nomination would be to force the others from the race. Yet on Wednesday, Gingrich reaffirmed his determination to stay in, which would leave Republicans with a pair of unappealing scenarios. The first is a drawn-out internal fight that, up to now, has often served to highlight Romney's shortcomings as a candidate. The other is a deadlock that runs all the way to the convention at the end of August, with potentially dire consequences for GOP chances against President Obama.
The prospective nominee would hope to spend the months after the primaries end in late June uniting the party, raising fresh campaign funds and turning voter attention toward the general election contest with Obama. A summerlong fight over delegate loyalties and party rules, and a nomination that remained unsettled until the convention for the first time since 1976, would squander the chance to turn the meeting in Tampa, Fla., into a vast campaign commercial.
"Modern political conventions are the most important political communications opportunities that the parties have, and to lose that opportunity is a huge problem. That's what we're talking about when we talk about taking the fight all the way to the convention," said GOP strategist Vin Weber, a Romney campaign advisor.
For Romney to bend the primary season narrative in a more positive direction, he should stay locked in on Obama's "failed economic policies," Weber said, adding: "This is an incredibly vulnerable president. Republicans have an excellent opportunity, provided we can refocus on him rather than on each other."
Exit polls show that Romney continues to face rejection from his party's conservative base.
"Some who are very conservative may not be yet in my camp, but they will be when I become the nominee," Romney told Fox News on Wednesday during a fundraising visit to New York. "What the nation wants is someone who understands the economy — not a, if you will, an economic lightweight," he added, referring to Santorum. (The former Pennsylvania senator was campaigning in Puerto Rico on Wednesday, ahead of Sunday's primary there.)
Romney pointed out that he extended his delegate lead this week despite third-place finishes in Alabama and Mississippi, thanks to caucus wins in Hawaii and American Samoa. But he still has fewer than half of the delegates needed to lock up the nomination. The most recent Associated Press count has Romney with 495 delegates to Santorum's 295. Gingrich is next with 131, and Rep. Ron Paul, who has yet to win a state, has 48.
The Santorum strategy boils down to depriving Romney of the nomination through a series of primary victories that steadily undermine confidence in the former Massachusetts governor. A string of Romney defeats could prompt defections from unbound delegates and party leaders who are automatic convention delegates.
Santorum's chances of pulling off that feat would improve if Gingrich, who has lost 26 of the last 27 contests, were to quit the race. By splitting the anti-Romney vote, Gingrich makes it more difficult for Santorum to achieve "momentum" wins, which generate waves of positive publicity.
With Gingrich out, Santorum could unify conservatives and get a clear shot at Romney. But at a subdued rally Wednesday in the outskirts of Chicago, Gingrich reaffirmed his intention not to quit.
"I am staying in this race," he told fewer than 100 people at the convention center in Rosemont. "I look forward to getting to Tampa with your help."