Ted Cruz and Bernie Sanders are aiming to inflict a rough night on their party front-runners in the Wisconsin primary.
Cruz hopes to haul in all or most of the 42 Republican delegates at stake Tuesday in a victory that would further complicate Donald Trump's path to the 1,237 delegates needed to secure the nomination before the GOP convention.
Sanders, meanwhile, is hoping to pull off his sixth win of the last seven state contests to undercut Hillary Clinton's claim that she has already amassed a decisive lead in the Democratic delegate derby.
The most recent polls show Cruz with a 10-point lead in the Republican race in the Badger state, as Trump seeks to recover from the roughest week of his campaign, which was strewn with missteps on abortion and controversial comments on national security.
"The entire country is looking at the state of Wisconsin," Cruz said in Milwaukee on Monday. "The people of Wisconsin, they're looking at the records of the candidates, and they realize that Donald screams and yells a lot, but he has no solutions. He has slogans, but no solutions," Cruz said.
Trump, however, is predicting that the polls are wrong.
"I hear the polls are busy. We could have a big surprise tonight folks, a big surprise. Feels like South Carolina, feels like New Hampshire, you're going to have a big surprise tonight," he said at a polling place Tuesday in Waukesha.
Such a scenario would be a disaster for Cruz, calling into question his claims that he has established himself as the only candidate with a realistic chance of stopping Trump.
Wisconsin was once seen as a favorable state for Trump since its Rust Belt manufacturing base has been hit by the migration of jobs to low-wage economies abroad and should be receptive to his criticism of global trade deals.
But the state is also a ripe target for Cruz because it has a highly engaged conservative electorate and talk radio network that was energized by Republican Gov. Scott Walker's election wins -- including a recall triumph -- and remains deeply politically engaged.
Based on the latest CNN delegate estimates, Trump has 740 of the 1,237 delegates needed to win the nomination. Cruz has 474 and Ohio Gov. John Kasich has 145.
Cruz only has a small mathematical chance of winning the nomination since a flurry of states voting before the end of April favor Trump. Kasich, who has won only one state, cannot reach the magic number in remaining contests.
But both men hope to win sufficient delegates to open the way to a contested convention. Trump currently needs to win 57% of the remaining 871 pledged delegates to clinch the nomination. If he walks away from Wisconsin without adding any delegates, that number rises to 60%, according to CNN estimates.
Facing a possible defeat in Wisconsin, and still trying to brush off his string of gaffes last week, Trump turned the focus Tuesday back to the issue that ignited his campaign in the first place --- illegal immigration. He issued a memo outlining a plan to bar undocumented Mexican immigrants from wiring money home to relatives if Mexico's government did not agree to pay $5-10 billion dollars to fund a border wall.
On the Democratic side, Sanders is aiming to capitalize on a hot streak to build up more momentum heading into the delegate-rich New York primary on April 19, where Clinton hopes to secure a win on home turf to maintain her big delegate lead.
But Sanders has a more complicated task than Cruz in slowing his party's front-runner, since Democratic delegates are doled out on a proportional basis -- rather than the winner-take-most formula used in Wisconsin by Republicans.
Still, the state should be a fertile one for Sanders, as it is similar to largely white battlegrounds where he has done well, has a long progressive tradition that should be a good fit with his grass-roots democratic socialism and has a strong population of students who have tended to side with him more than Clinton.
The Vermont senator's campaign manager Jeff Weaver on Tuesday deflected Clinton campaign arguments that the former secretary of state already has an insurmountable delegate lead by suggesting Sanders could emerge with the nomination at the convention.
"If you look at the math, if you want to talk about math, the truth is that it is very, very, very unlikely that either candidate, either Secretary Clinton or Sen. Sanders, will go into the convention with a majority needed of pledged delegates in order to win," Weaver told CNN's Chris Cuomo on "New Day."
Clinton and Sanders are chasing their magic number of 2,383 delegates to win the nomination. Clinton currently has 1,742 total delegates -- 1,259 of whom are pledged or bound to vote for her and 483 super delegates who have said they support her but theoretically could switch allegiances. Sanders has 1,051 total delegates, including 1,020 pledged and 31 super delegates.
"I think it'll be an interesting Democratic convention," Weaver said.
But Robby Mook, Clinton's campaign manager, suggested the map favors Clinton, who is targeting big wins in delegate-rich areas in the weeks to come.
"There are a lot of contests coming up, there are three very delegate-rich states coming up, Pennsylvania, New York and then California," he told CNN's John Berman on "New Day." "I think there are plenty delegates for one candidate to get a majority of pledged delegates."