It’s primary day in Illinois – and former senator Rick Santorum’s (R-Pa.) campaign is marking the occasion by throwing the kitchen sink at former Massachusetts governor Mitt Romney (R).

First, Santorum senior adviser John Brabender took aim Monday morning at Romney’s tenure at Bain Capital – months after Santorum defended Romney against similar attacks by Newt Gingrich and Rick Perry. Santorum himself derided Romney as a “Wall Street financier” at a campaign event Monday afternoon.

Then, Santorum spokeswoman Alice Stewart resurrected the decades-old story of Romney’s dog, Seamus, who the former Massachusetts governor infamously placed in a carrier on top of the family car on a trip to Canada in the 1980s.

Will Santorum’s mud-slinging pay off? Given that he’s spending his primary night in Pennsylvania while Romney will be in Illinois, it would appear that Santorum isn’t all too confident of a win in the Land of Lincoln.

And even if he does win, there’s still the matter of the former Pennsylvania senator’s delegate woes – he’s ineligible for delegates in four of 18 Illinois congressional districts.

We’ll be liveblogging here as tonight’s primary results roll in – stay tuned.

Here’s a closer look at today on the trail (Courtesy of candidate schedules and the PBS NewsHour Political Calendar; all times Eastern):

9:30 a.m.: Newt Gingrich holds a meet-and-greet in Shreveport, La.

Noon: Newt Gingrich holds a town hall in Ruston, La.

2:30 p.m.: Ron Paul holds a luncheon fundraiser in Burbank, Calif.

4:30 p.m.: Newt Gingrich holds a meet-and-greet in Monroe, La.

8 p.m.: Rick Santorum holds a primary-night party in Gettysburg, Pa.

9:30 p.m.: Mitt Romney holds a primary-night event in Schaumburg, Ill.

11:30 p.m.: Ron Paul appears on The Tonight Show with Jay Leno.