(CBS News) CHICAGO - Mitt Romney, capturing all of the commonwealth's twenty delegates. Rick Santorum was second.
CBS News correspondent Jan Crawford reports that next up is Tuesday's contest in Illinois, where 54 delegates are at stake in the latest test for front-runner Mitt Romney.
"The people of Illinois have an opportunity in this primary to really send shock waves through the establishment moderate Republicans," Santorum told a rally of supporters recently.
With the Republican race closer than most would have imagined, Illinois matters. Campaigning this weekend in southern Illinois, Rick Santorum targeted social conservatives.
"If we're able to come out of Illinois with a huge or surprise win, I guarantee you, I guarantee you that we will win this nomination," Santorum said.Special Section: Campaign 2012
But Santorum has an uphill battle. Romney is expected to do well in Chicago and its suburbs, which make up half of the Republican vote.
"I understand how the economy works, not because I debated it in Congress," Romney said recently.
Romney argues that he, not the former senator, is the only candidate who has what it takes to beat the president.
"We're not going to be successful in replacing an economic lightweight if we nominate an economic lightweight. And I'm an economic heavyweight, I know how this economy works," Romney said.
As usual, Romney is out-spending Santorum, blanketing the airwaves with attack ads focusing on what he calls Santorum's weakness, "the economy."
Another problem for Santorum is that he failed to qualify for delegates in four Illinois congressional districts and is eligible for only 44 of the state's 54 delegates in play.
But he vows to fight for the 1,144 delegates needed to claim the nomination, all the way to the Republican convention.