CNN is projecting that Ted Cruz will win the Republican primary in Wisconsin, while Bernie Sanders is holding a lead on the Democratic side.
Sanders is hoping to pull off his sixth win of the past seven state contests to undercut frontrunner Hillary Clinton's claim that she has already amassed a decisive lead in the Democratic delegate derby, the network noted.
The most recent polls heading into the contest showed Cruz with a roughly 10-point lead in the Republican race in Wisconsin, as Trump seeks to recover from the roughest week of his campaign, which was strewn with his statement on abortion and controversial comments on national security.
Speaking on WISN radio in Milwaukee earlier on Tuesday, Cruz predicted a "strong victory" in Wisconsin that would be a "powerful step" toward uniting the Republican Party.
Trump, however, is warning that the polls are wrong in the state's open primary — a type of election that can be unpredictable because registered voters can choose to vote for candidates from either side of the political aisle.
"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, Wisconsin, according to CNN.
On the Democratic side, Sanders is aiming to capitalize on a hot streak to build up more momentum heading into the New York primary on April 19, where Clinton hopes to secure a win on home turf to maintain her big delegate lead.
Earlier on Tuesday, a Reuters poll found that Cruz has pulled into a statistical dead heat with Trump.
Cruz got 35.2 percent of support to Trump's 39.5 percent, the poll of 568 Republicans taken April 1-5 found.