According to Rasmussen, Romney has opened a comfortable 9 point lead in Illinois in advance of the primary there on Tuesday.

A Fox News poll has it a little closer; Romney by 6 points.

RCP:

Nonetheless, 32 percent of those surveyed say they could change their minds by Tuesday, signaling a somewhat fluid contest.

Romney leads Santorum by nine points among men and eight points among women. The former Massachusetts governor leads across all age groups, but takes seniors by double digits. Santorum leads by eight points among the most conservative voters, while Romney leads by 20 points among those who identity as somewhat conservative.

Sixty-eight percent view Romney favorably while 30 percent have a negative opinion of him. Santorum's favorability rating is virtually the same. Gingrich gets a positive net of 8 percent while Paul receives a negative net of 23 percent.

Romney released a television ad Friday in Illinois attacking Santorum as "The Wrong Choice." And a super PAC supporting Santorum has taken to the airwaves with a reported $310,000 ad buy, going after Romney for signing Massachusetts' health care law.

Meanwhile, a Fox Chicago News poll finds a closer race, with Romney leading the former Pennsylvania senator, 37 percent to 31 percent. Gingrich attracted 14 percent while Paul took 8 percent. Ten percent remain undecided.

The survey found the candidates running virtually even among men and women. Notably, 47 percent say they are dissatisfied with their choices for the GOP nomination, while 43 percent are content with the field.

Turnout will be critical - not just how many but where those votes will come from. Romney is expected to do well in the Chicago suburbs and collar counties bordering Wisconsin and Indiana. Santorum can be counted on to do well downstate. There are more votes for Romney out there but if he can't motivate his people to show up at the polls, Santorum could squeak by.

Unfortuntaely, Santorum will lose delegates as a result of the complicated manner in which they are awarded. Rick has failed to field a full delegate slate and can win a maximum of 44 out of the 54 delegates at stake (15 additional delegates will be awarded at the state convention). Even if Santorum wins the primary, he will likely lose the delegate race.