WASHINGTON (AP) -- The GOP presidential race veered offshore to Puerto Rico, where 20 delegates were in stake in Sunday's primary but residents cannot vote in the general election.
While fighting for votes in the U.S. territory, Mitt Romney and Rick Santorum already shifted their focus to upcoming primaries in Illinois and Louisiana. Front-runner Romney held a sizable edge in delegates, cash and campaign organization, but Santorum hoped for a drawn-out nomination fight through the summer that would deny Romney the clincher and set up a contested party convention in August.
"One of the great blessings I've had in every political campaign is people underestimate me, people underestimate what God can do," Santorum told a church audience in Louisiana.
Romney and Santorum criticized the other from afar as they looked ahead to Tuesday's primary in Illinois and Louisiana's contest on Saturday. GOP rivals Newt Gingrich and Ron Paul both remained in contention, too, but seemed overshadowed by the Romney-Santorum rivalry.
"This is a primary process where somebody had a huge advantage, huge money advantage, huge advantage of establishment support and he hasn't been able to close the deal and even come close to closing the deal," Santorum said of Romney. "That tells you that there's a real flaw there."
Santorum faces his own flaws. He badly trails Romney in fundraising. His organization is a shadow of Romney's and his advertising a fraction of what's airing in support of the former Massachusetts governor.
"In a campaign, one of the things you recognize from Day One is that you need to organize a financial operation to make sure you can run the campaign," Romney said.
"We have to have a nominee who has the capacity and the organization necessary to raise money to be competitive. I intend to be very competitive with President Obama, to make sure that we get our message out, we defeat him. This is not about a shoestring operation," Romney said.
The latest test was Puerto Rico, where 20 delegates were up for grabs in the race for the 1,144 delegates needed to win the nomination and face President Barack Obama in the general election. As the day began, Romney had 501 delegates in his camp and Santorum had 253, according to The Associated Press' tally. Gingrich trailed with 136 delegates and Paul had 50.
"Why, with tens and hundreds of millions of dollars, hasn't he been able to do anything to get this nomination even close to cemented away?" asked Santorum, a former senator from Pennsylvania.
Romney is on pace to capture the nomination in June. Both say they would try to force the nomination to a fight in Tampa and turn the convention into more than a glossy advertisement for the party for the first time since 1976. Romney's aides said that was a fantasy scenario, but they are working hard to prevent it.
"I can't tell you exactly how the process is going to work," Romney said. "But I bet I'm going to become the nominee, I sure hope I'm going to become the nominee."
With half the states yet to weigh in on the Republican presidential nomination, the question of how likely some serious delegate trading would go on at the national convention in Tampa is being asked more frequently.
Republican National Chairman Reince Priebus insisted that his party will have a nominee sooner rather than later.
"We're only at half time," Priebus said. "I think that this process is going to play itself out. We will have a nominee, I think, fairly soon -- one, two months away."
Puerto Rico was unlikely to reset the course of the campaign. Both Romney and Santorum visited the island but did not invest the millions of dollars in advertising that has been the hallmark of other contests. Instead, they darted to upcoming states such as Louisiana and Illinois, where polls show Romney's advantage.
Romney launched twin attacks against Obama and Santorum Sunday morning as supporters ate pancakes at the American Legion hall in Moline, Ill., a city set on the Mississippi River along western Illinois' border with the Iowa.
"He's an economic lightweight," Romney said of Obama. "It's time to put in place an economic heavyweight, and I am."
And just as Santorum has linked Romney to Obama in recent days, Romney returned the favor during his brief morning address, the first of three public stops Sunday in the home state of the GOP's first president, Abraham Lincoln.
"Sen. Santorum has the same economic lightweight background the president has," Romney said, adding that Santorum once supported spending $500,000 for a polar bear exhibit in Pittsburg.
Asked about his odds in Illinois, Santorum was curt.
"Keep working," Santorum said after services at a Bossier City, La., church. "That's all we can do."
As voting began in Puerto Rico, Santorum visited a pair of churches in Louisiana and appealed to social conservatives, sharing how his faith has shaped his political career and his opposition to abortion rights and gay marriage. He didn't mention Romney or any of his other Republican opponents during talks at both churches.
Faith alone, however, doesn't fuel a successful presidential campaign. Santorum does not have a campaign headquarters, has refused to hire a pollster or speechwriter and is not even on the ballot for the Washington, D.C., primary on April 3. He also has failed to submit full slates of potential delegates to some states, leaving some of his victories hollow.
"You know, during the time that these delegates had to be filed for these states, I was driving around in a truck with a guy named Chuck in Iowa, you know, breathing through a Swizzle Stick and running a marathon," Santorum said.
In Puerto Rico, turnout appeared light and officials predicted about 150,000 people would cast ballots in the Republican primary.
Among them was Francisco Rodriguez, a 76-year-old architect who was supporting Romney, in part because Romney had secured the endorsement of Gov. Luis Fortuno and other leading politicians.
"He has a stronger connection to Puerto Rico and that will help us in the process of becoming a state," Rodriguez said.
He had kind words for Santorum, describing him as a "person of faith, a good Catholic." But he said he thinks the former senator hurt himself with his statements that English would have to be the official language if the U.S. territory were to seek statehood.
"In Puerto Rico, we get along fine with both languages," Rodriguez said.
Santorum spoke with CNN's "State of the Union" and ABC's "This Week." Romney appeared on "Fox News Sunday," and Priebus was interviewed on CBS' "Face the Nation."
Associated Press writers Andrew DeMillo in Bossier City, La., and Kasie Hunt and Ben Fox in San Juan, Puerto Rico, contributed to this report.