SPRINGFIELD, Ill. (AP) - An increasingly confident Mitt Romney called President Barack Obama an "economic lightweight" Monday as the Republican presidential candidate looked beyond Tuesday's Illinois primary to a general election showdown with the incumbent Democrat.
Romney's chief rival - Rick Santorum - kept the focus on the GOP front-runner, arguing that nominating the former Massachusetts governor would deprive the party of a defining issue to use against Obama in the November election - health care.
"Obamacare," Santorum said, was based on "Romneycare," Massachusetts' 2006 health care law.
Courting voters in Obama's home state, Romney acknowledged that the economy was moving in the right direction as hundreds of thousands of jobs have been created, the unemployment rate has dropped and consumer confidence has jumped. Romney suggested it was in spite of the president.
"The economy always comes back after a recession of course," said Romney, previewing what could be a general election argument. "There's never been one that we didn't recover from. The problem is this one has been deeper than it needed to be and a slower recovery than it should have been."
The former venture capitalist said he's better equipped to steer the economy.
"There are dramatic differences between me and President Obama," Romney said during a morning campaign stop at Charlie Parker's diner in Springfield. "I'm not an economic lightweight. President Obama is."
Romney extended his delegate lead Sunday in Puerto Rico, where he trounced rival Rick Santorum and scored all 20 of the Caribbean island's delegates.
Romney has collected more delegates than his opponents combined and is poised to win the delegate battle in Illinois, even if he loses the popular vote, thanks to missteps by Santorum's shoestring operation.
Brushing aside skepticism from the party's right flank, Romney aides have been emphasizing their overwhelming mathematical advantage in the race to 1,144 delegates - the number needed to clinch the GOP presidential nomination and face President Barack Obama in the fall.
Santorum has all but conceded he cannot earn enough delegates to win, but claimed he was in contest for the long haul because Romney is a weak front-runner.
"I looked at the leading candidate for president on the Republican side and I said 'He can't be the nominee,'" Santorum told several hundred people at the Venetian Club in Rockford. "He can't be the nominee because he would take away from the Republican Party in this crucial election, the most important in your lifetime, he would take away the central issue in this campaign. He is uniquely disqualified to go and make the case against Obamacare because he developed the blueprint for Obamacare."
In 2006, then-Massachusetts Gov. Romney instituted a sweeping health care system in the state that required everyone to have insurance.
It was the model for Obama's divisive health care overhaul that he signed into law two years ago this Friday.
"Why Illinois would you consider voting for someone for president on the Republican side who is for Romneycare, the blueprint for Obamacare, and for government mandates?" Santorum asked. ".... . He will give every single important issue on this subject matter away. There is no difference between the two."
He also accused Romney of forcing Catholic hospitals to provide the morning-after pill when he was governor. Santorum argued that the pill "caused abortion."
As a gubernatorial candidate in 2002, Romney signed a Planned Parenthood questionnaire that he supported using state tax dollars to fund abortion services through Medicaid for low-income women, according to a copy of the questionnaire.
He also pledged support for increased access to emergency contraception such as the "morning-after pill," which he now condemns as an "abortive pill." Santorum said that he'll "go out and compete in every state," calling Illinois a "two-person race."
"What I've said is, I think it's going to be very difficult as this goes on for anybody to get that magic number" to clinch the nomination, Santorum said in an interview on CBS's "This Morning."
Santorum called Romney a "big-government heavyweight," responding on MSNBC Monday to the former Massachusetts governor's recent assertion that he couldn't match up on economic expertise.
Santorum told CBS he thinks the chances of a brokered GOP convention in August "are increasing."
In nationally broadcast remarks Sunday, Santorum sidestepped when asked if he would fight Romney on the convention floor if he failed before August to stop the former Massachusetts governor from getting the required number of delegates.
Romney aides privately likened the situation to the Black Knight in "Monty Python and the Holy Grail" who loses his arms and legs in battle with King Arthur but insists he has only a flesh wound.
The Romney camp suggested that Tuesday's performance would extend Romney's delegate advantage, even if he loses the popular vote. Santorum cannot win at least 10 of the state's 54 delegates because his campaign failed to file the paperwork.
Polls suggest a Romney edge in Illinois. At a Romney campaign stop Sunday, voters were divided.
"I'm leaning toward Santorum, but I wanted to hear him in person," said Nichole Warren, a 32-year-old stay-at-home mom from nearby South Beloit. "I hear (Romney) talk and I hear a lot of Obama in him, and that scares me."
But Sid Haffenden, a 61-year-old retired toll-way worker, said, "Santorum has too much baggage." He added, "I want a businessman."
At this rate, Romney is on pace to capture the nomination in June unless Santorum or former House Speaker Newt Gingrich is able to win decisively in the coming contests.
Both have said they would stay in the race and perhaps force the nomination to a fight at the GOP's convention in Tampa if Romney doesn't amass enough delegates to arrive with a mandate.
That would turn the convention into an intra-party brawl for the first time since 1976. Including Puerto Rico's results, Romney has now collected 521 delegates, compared to Santorum's 253, Gingrich's 136 and Paul's 50, according to The Associated Press count.