EFFINGHAM, Ill. — Rick Santorum on Saturday morphed his chief rival for the Republican presidential nomination into the incumbent Democrat both are fighting to unseat, calling the two indistinguishable on key issues of the day.
Santorum, looking for another primary shocker in Illinois on Tuesday, lumped together front-runner Mitt Romney and President Barack Obama on everything from health policy to fossil-fuel regulations.
"People ask me why I am the best candidate to run against Barack Obama," Santorum said. "I feel like in some respects like I am running against Barack Obama here in this primary because Mitt Romney has the same positions as Barack Obama in this primary."
Santorum, the former Pennsylvania senator, homed in on a part of Illinois where he stands the best chance to rack up votes in Tuesday's Republican primary. It's the next big battle in his blow-for-blow nomination battle with the former Massachusetts governor.
Santorum's most piercing words came on health care, reminding the tea party-heavy crowd that Massachusetts enacted an insurance mandate that some regard as a template for the national law foes deride as Obamacare.
Santorum has ramped up his criticism of Romney as the Supreme Court readies for an unprecedented three days of oral arguments on the constitutionality of the federal law. He said Romney won't be able to effectively combat Obama on the issue as the GOP nominee.
"How long does he talk about Obamacare and the fact that he'll repeal it? Oh, he puts out that one-liner. But does he really get into the core issues?" Santorum said. "No. Because he can't."
Likewise, he likened Romney's moves to regulate carbon emissions to what he called a strategy out of former Vice President Al Gore's anti-global warming playbook.
Santorum spoke in the warehouse of an 87,000-square foot factory that makes high-end butcher's blocks.
It was the first of three events in southern Illinois, an area dotted with farms and small, industrial cities. He had concentrated on suburban Chicago Friday.
Santorum is banking on a strong showing in the downstate region, where the GOP electorate better suits his strongly conservative stances. Most of the state's population, however, lives in the Chicago area.
Luke Parr, an accountant from Greenup, Ill., gravitated to Santorum after his first choice, Texas Gov. Rick Perry, left the race. Parr said he believes Santorum, once in office, would keep the promises he makes while campaigning. It's a level of trust Parr doesn't have for Romney.
"He drives on both sides of the road. Someone is going to get hurt, probably the people who vote for him," Parr said of the former Massachusetts governor.
Earlier Saturday, Santorum was in the St. Louis area, mining for last minute support as Missouri Republicans gathered in local caucuses, the first step in determining how the state's 52 presidential delegates will be committed at the national convention in August.
Santorum won the state's nonbinding primary last month and was the only one of the four Republican presidential candidates visiting caucus sites Saturday. Former Massachusetts Gov. Mitt Romney and Texas Rep. Ron Paul also campaigned in Missouri earlier in the week. Former House Speaker Newt Gingrich skipped the state.
No winner will be declared from the nearly 140 local caucus meetings Saturday. That's because the state party rules do not require local delegates to be bound to any candidate, and no straw poll is being conducted. Saturday's meetings will elect 2,123 people to advance to congressional district conventions on April 21 and a state convention on June 2. It's at those meetings that most of Missouri's 52 delegates will be bound to presidential candidates.
Santorum, Romney and Paul were nonetheless urging supporters to attend the local caucuses, hoping to advance a slate of backers to the district conventions.
"Delegates. It's as simple as that. They matter," Santorum said, after an early morning visit to a caucus site at the Westminster Christian Academy in St. Louis.
Mixed among his supporters at the school were dozens of people with Romney signs planning to challenge local Republican leaders trying to elect a slate of Santorum delegates.
Norman Baxter, 77, a retired corporate communications officer who is the Republican committeeman for the local township, is among those pushing the Santorum slate.
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"I'm a conservative — a strong conservative — and I think Santorum represents a lot of the values that I think are very, very important to the survival of this country," Baxter said.
Romney maintains a big advantage in the race for Republican National Convention delegates, with 495 to Santorum's 252, but is still a ways away from the 1,144 needed for nomination.
Former House Speaker Newt Gingrich and Texas Rep. Ron Paul, both of whom swung through Illinois earlier in the week, are also on Tuesday's ballot. But Gingrich has turned most of his attention to Louisiana, which votes next Saturday.
Associated Press writers Jim Salter in Wildwood, Mo., contributed to this report.