CHICAGO - Republican White House hopefuls waged battle Saturday for Illinois as the primary in President Barack Obama's home state loomed as the next key test for candidates.
Weekend votes were also being held in Missouri and the territory of Puerto Rico, but Illinois appeared to be a new gut check for Republicans struggling to keep momentum in the race for the nomination to challenge Obama in November.
Polls showed former senator Rick Santorum within striking range in Illinois of frontrunner Mitt Romney, who has a commanding lead in the all-important delegates count but has been weakened by his failure to clinch the nomination.
Romney scheduled a series of events in Illinois Sunday starting with a pancake breakfast in Moline, followed by a gathering with voters in Rockford and a town hall meeting in Vernon Hills.
Santorum meanwhile kept up a frenetic pace, with events Saturday in Missouri and Illinois, before flying Sunday to Louisiana, which holds a primary March 24. He was due back in Illinois for more campaigning Monday.
The fierce Republican campaign came as Obama flew home to Chicago Friday for a lucrative fundraiser with his Democratic Party, upping efforts to pad its re-election campaign warchest.
In Illinois, which votes Tuesday, Santorum took direct aim at Obama in a speech to a suburban Chicago high school, where he drilled into the president's policies.
"You have a president of the United States who does not believe America was a great country until the government took money from you and redistributed it back to others," Santorum said.
"America is great because it was founded great."
Santorum, a devout Roman Catholic and opponent of abortion and gay marriage, is seen as the most conservative Republican candidate vying to take on Obama in November, but his ability to win over centrist and independent voters is doubted.
The former Pennsylvania senator is making an aggressive push in Illinois, adding campaign stops and launching ads attacking Romney for raising taxes while governor of Massachusetts and supporting the Wall Street bailout and government control of health care.
Romney has responded by pouring millions of dollars into local ads and moving up plans to campaign in Illinois.
"Right now, under Barack Obama, the federal government is standing in the way of economic recovery," Romney said. "I have a plan to get it out of the way and get the economy growing."
A Santorum victory in Midwestern, industrialized Illinois could prove a far more significant upset than his recent wins in the Deep South states of Alabama and Mississippi, where evangelical voters carry more weight.
It would also give Santorum important momentum going into Louisiana and contests in Wisconsin, Maryland and Washington DC on April 3.
Romney before settling into the Illinois fight dropped into Puerto Rico ahead of its Sunday primary. The island is being courted by Republican candidates, in part because the broader US Hispanic vote is seen as crucial.
Santorum found himself in hot water this week over suggesting the territory would need to make English its official language before it could become the 51st US state.
English and Spanish are currently recognized there, and Romney told reporters in Puerto Rico -- where he held a raucous street rally in San Juan Friday night -- that the island's language status need not be changed in order to seek statehood.
Some Missouri counties were meanwhile holding Republican caucuses Saturday to elect convention delegates.
Santorum won what was largely a beauty contest there last month, but rival Romney has upped his effort, telling Missouri voters they "have a chance to take a step toward changing the direction of our country."
The outcome of the caucuses will not be immediately clear, based on party rules.
Former House speaker Newt Gingrich has vowed to take the battle all the way to the Republican convention in August, ignoring increasing pressure to drop out and consolidate the conservative vote behind Santorum. Also hanging on is libertarian Congressman Ron Paul of Texas.
Proportional distribution of delegates will make it difficult for Romney to reach the magic number of 1,144 before May or even June, but many analysts forecast he will be the eventual nominee.
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