Polls showed former senator Rick Santorum within striking range of frontrunner Mitt Romney, who has a commanding lead in all-important delegates but has been weakened by his failure to clinch the nomination.
The fierce GOP campaign was being waged as Obama flew home to Chicago for a fundraiser as his party, sensing a tight election, is upping its effort to gain traction with voters.
In some counties of Missouri, Republican were holding their caucuses on Saturday to elect convention delegates. But the outcome of the meetings was not expected to be immediately clear because under local party rules, the delegates were not bound to support specific presidential contenders.
Obama took a short swipe at his rivals after screening a laudatory 17-minute documentary on his presidency that was launched on Thursday.
He welcomed them to the “land of Lincoln” and said he hoped some of the first Republican president’s ideals – an understanding of the importance of the federal government and a belief that we are “one people and we rise or fall together” – would “rub off on them.”
“You may not feel confident that will happen,” Obama told supporters gathered at Chicago’s historic Palmer House hotel.
“You may be watching some of this avalanche of attack ads and think this is not appealing to the better angels of our nature. But hope springs eternal.”
Santorum took direct aim at Obama in a speech to a suburban Chicago high school that showed a very different understanding of the role of government.
“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 castigated Obama for believing that it is the role of elites in government to “better organize society” and promoting a culture of dependence and entitlement rather than to allow people the freedom and opportunity to succeed or fail on their own terms.
“There will be inequality, but the key to America is do you have the opportunity to go from not having much to having great amounts of wealth. That is still the case in America.”
Santorum, a devout Catholic and opponent of abortion and gay marriage, is seen as the most conservative Republican candidate vying to take on Democrat Obama on November 6, but his ability to win over centrist and independent voters is doubted.
A Santorum victory Tuesday in this midwestern, industrialized state could consequently 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 the southern state of Louisiana’s primary March 24 and contests in Wisconsin, Maryland and Washington DC on April 3.
The former Pennsylvania senator is making an aggressive push in Illinois, adding many campaign stops and launching ads attacking Romney for raising taxes and supporting the Wall Street bailout and government control of healthcare.
Romney responded by moving up plans to campaign in Illinois – greeting voters at a pancake house early Friday before flying to Puerto Rico ahead of caucuses there Sunday – and pouring millions of dollars into ads for the local airwaves.
His campaign is blasting Santorum as a Washington insider and “economic lightweight” without the ability to defeat Obama or handle the challenges of the presidency.
“The Santorum campaign has been based on hot rhetoric,” former New Hampshire governor John Sununu, a Romney supporter, told reporters.
“Good rhetoric without a capacity to perform is just a Republican Obama.”
The campaign’s new intensity comes at a moment of high volatility in American politics, with Obama’s approval rating lurching up and down in several polls, partly influenced by rising gasoline prices.
But the consistently divisive Republican race has been an unexpected boon for Obama and it could continue for weeks if not months to come.
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.
The proportional distribution of delegates will make it difficult for Romney to reach the magic number of 1,144 before May or even June.
For the same reason, Santorum also is unlikely to capture enough delegates to clinch the nomination, but he could win enough to justify a brokered convention.
“Barring a massive, difficult to fathom shift in this contest, Mitt Romney has a better than 80 percent chance to be the GOP nominee,” Larry Sabato, director of the University of Virginia’s Center for Politics, wrote in an analysis of the delegate math.