Voter turnout is light in Illinois, according to state officials, despite several competitive congressional primaries, the undecided GOP presidential contest and near-perfect spring weather.

Mitt Romney and Rick Santorum campaigned hard in the Land of Lincoln ahead of Tuesday's vote, but the contest seemed to loss steam as a slew of polls released Monday showed Romney leading in the state.

Santorum's team has been downplaying expectations for their candidate — and thereby building them up for Romney. Santorum is scheduled to spend Primary Night in his home state of Pennsylvania.

Romney is set for an Election Night rally in Schaumburg, Ill., a contrast to last week's contests in Alabama and Mississippi, where no rally was scheduled and Santorum won both Southern states.

A victory in Illinois Tuesday night would be the first state Romney's won in two weeks (he won the territory of Puerto Rico on Sunday). It also represents an opportunity for the former Massachusetts governor to prove he can earn a commanding win in a Midwestern state and regain his footing as the inevitable GOP nominee. A strong showing in the conservative Chicago suburbs would demonstrate that he can appeal to the type of voters who will likely swing a general-election showdown with President Obama.

Romney heavily outspent Santorum in Illinois, where an expensive media market in Chicago made competing in the ad wars difficult for the former senator.

An upset Santorum win, however, would deal a serious blow to Romney's campaign, which has struggled to convincingly put away the nomination. While Santorum is unlikely to take away more delegates than Romney — his campaign failed to file a full slate of candidates in the state — a win of the popular vote would underscore the reluctance of Republicans to coalesce around the former governor's campaign.

Romney criss-crossed the state Monday, hitting on economic themes during speeches at the University of Chicago and in Springfield. While Romney focused his remarks on criticism of the president — denouncing his "assault on economic freedom" at the University of Chicago, where Obama taught law — he also doubled down on criticism of Santorum's economic record.

"We're going to have to replace [President Obama] with someone who knows how to run this economy," Romney told voters in Springfield.

Santorum acknowledged that he faced an uphill battle in a state expected to demographically favor Romney.

"It's going to be a tight race," Santorum said while campaigning Monday in Dixon, Ill., the hometown of former President Reagan, according to Bloomberg. "I've learned not to underestimate the folks out here, how hard they are working, and the energy and enthusiasm that's built around a positive message, as opposed to one that's just out there hammering away and being negative."

But convincing voters to head to the polls was proving elusive, despite clear skies and temperatures topping 80 degrees in heavily Republican Chicago suburbs like Park Ridge and Wheaton. Local election officials were reporting light turnout in the early afternoon, mirroring a trend in other recent GOP primaries.

The low turnout should add to the unpredictability of a string of competitive congressional primaries, the result of Illinois's recent redistricting, in which it lost one House seat.

Ten-term Republican Rep. Don Manzullo is facing off against freshman Rep. Adam Kinzinger in a bruising primary fight that has evolved into a battle between the Tea Party and the GOP establishment. Manzullo told The Hill Monday that he thought House Majority Leader Eric CantorEric CantorEric Cantor offering advice to end ‘immigration wars’ Trump's olive branch differs from the golden eras of bipartisanship After divisive rally, Trump calls for unity MORE (R-Va.) should resign his leadership position after backing Kinzinger. The winner of the primary will not face a Democratic challenge in the fall, and is a near-lock to return to Congress.

Rep Jesse Jackson Jr. (D-Ill.) is also facing a tough primary battle with former Rep. Debbie Halvorson. Jackson has been dogged by ethics charges and the admission of an extramarital affair. And his district was redrawn to include large swaths of the area Halvorson used to represent, giving Jackson his first competitive contest since being elected to Congress in the 1990s.

Other contests include a Democratic showdown for the right to challenge Rep. Joe Walsh (R-Ill.), an outspoken Tea Party freshman many Democrats view as vulnerable, and an open primary to replace Rep. Jerry Costello (D-Ill.), a popular downstate congressman who has served longer than anyone else in the Illinois delegation. Costello's district includes a chunk of the conservative St. Louis suburbs, and Republicans believe they could pick up the seat in November.