Besides presenting possible problems for Trump, a win would also be significant for Cruz himself.
Cruz said that the primary would cap off an "incredible two weeks" for his campaign and described it as a way to prevent Trump from securing the nomination and stopping Hillary Clinton from getting back in the White House.
"A victory here tomorrow will resonate across this country, will change the outcome in states to come all across this country," he said at a rally Monday.
In a potentially telling move, Cruz is the only one of the three Republican candidates to plan an election night event tonight.
Bringing in Big Delegate Numbers
So far, the Texas senator's biggest claim to victory was a home-state win, which brought him a three-digit delegate jackpot.
If he wins tonight, it would be the next-largest delegate state to his name. Wisconsin has 42 delegates at stake for the Republicans and candidates have the potential to take all. But in order to do so, he would need to win both the statewide vote and all of the state’s congressional districts.
The next biggest victories Cruz claimed were Utah and Kansas, which had 40 delegates a piece.
Even if tonight is a sweep for Cruz, that still doesn't mean that he has an easy chance of reaching the required 1,237 delegates needed to secure the nomination.
As a result, a Cruz win could lead to a greater likelihood that the Republicans will face a contested convention, where no candidate gets to 1,237 delegates.
"Bernie Sanders has a better chance in passing Hillary Clinton among pledged delegates than Ted Cruz does in passing Donald Trump," ABC News political analyst Matt Dowd said on "Good Morning America" today.
According to ABC News’ estimates, Trump has a total of 737 delegates and Cruz has 475 total delegates (including superdelegates), meaning that they would need 500 and 762 delegates respectively to secure the nomination. For Trump, that would mean that he needs to win 57 percent of the coming contests, while Cruz would need to win 87 percent.
Gov. John Kasich has 143 total delegates and it is mathematically impossible for him to secure the nomination without a brokered convention in July.
Pumping Up Support
Cruz's supporters see a possible win tonight as a sign that he's only growing with time.
Elliott Abrams, a senior fellow for Middle Eastern studies at the Council on Foreign Relations, has been a Cruz supporter for months.
"A Wisconsin victory will more clearly show that he is growing in popularity and support," Abrams told ABC News.
"Six months ago no one would have said 'Ted Cruz will win Wisconsin.' A victory would be a reminder of the expanding circles of support for him, and a reminder of what a great campaign he has run," he said.