Both Mitt Romney and Rick Santorum have many events scheduled between now and next Tuesday.
The candidates were in the Chicago suburbs Friday. Romney was joined by New Jersey Governor Chris Christie and Santorum had three stops in Arlington Heights.
Santorum trails Romney by a 2-to-1 margin in the delegate count, so Illinois is seen by many as a must-win for him.
Friday night, in the backyard of President Obama's hometown, Santorum charged up a crowd of conservative voters.
"You have a unique duty here in Illinois to correct a wrong," Santorum said.
At one point during his speech, Santorum was interrupted by hecklers protesting his opposition to gay marriage.
The former Pennsylvania senator appeared unfazed and continued his attack on the White House.
"Ladies and gentleman we are the greatest nation in the history of the world, and we have a president who doesn't believe that," he said.
Santorum's first appearance Friday was before a packed auditorium of students at Hersey High School.
"I think we have a country right now that, as you realize, is divided on many fronts," Santorum said. "And I would make the argument that this president has done nothing to try to heal any of those divides and in fact has exacerbated them."
After his speech, the former Pennsylvania Senator took prescreened questions from three Hersey students.
At one point, Santorum, who has a special needs child, appeared irritated when 17-year-old Stefan Vucicevic twice asked whether the President's health care law is a benefit to less affluent parents of disabled children.
"I'm not too sure I understand your question," Santorum said. "They can apply for Medicaid and receive Medicaid services and have those services provided to their child."
"He looked really uneasy," said Vucicevic. "He wasn't comfortable at all. He kind of just said that, you know, all families can get Medicaid, but I don't think that's the case. Not everyone qualifies for it."
Santorum's appearances in Arlington Heights come as Romney is hitting him on the economy in a new TV ad in Illinois.
Romney and his allies are outspending Santorum 7-to-1 on Illinois' airwaves.
At a Rosemont restaurant Friday, Romney mixed politics and pancakes while blasting President Obama.
"The number one issue in America, the strength of our economy, the ability to have good jobs with rising incomes, the ability to get gasoline and energy at reasonable prices," Romney said. "This all collectively what I'll call the economy and on that issue, this President is a lightweight.
The former Massachusetts Governor also has surrogates campaigning in Illinois ahead of Tuesday's primary, including New Jersey Governor Chris Christie, who was at Elmhurst College today.
"We need to get back to having you make the decisions, not the people in Washington, DC," Christie said.
Santorum does have some Chicago area roots. He graduated from Carmel High School in Mundelein after attending his senior year there. Saturday, he is scheduled to campaign in the St. Louis area before making downstate Illinois stops on Sunday.