Wisconsin Primary Could Be Key to Contested Convention

Tuesday's vote in Wisconsin could not only help shore up the momentum for candidates on both sides of the presidential race, but it could also determine whether the Republicans are headed to a contested convention.

Neither Donald Trump nor Hillary Clinton, their respective party's front-runner, is ahead in the latest polls in Wisconsin, where Sen. Ted Cruz is leading Trump by 10 percentage points and Sen. Bernie Sanders is leading Clinton by 4 points.

If that polling, released by Marquette University last week, holds true and Cruz wins Tuesday, Trump's inevitability might be in jeopardy, ABC News political analyst Matthew Dowd said.

"If he would win Wisconsin, he likely gets it, if he loses Wisconsin he likely doesn't," Dowd said of Trump's securing the nomination outright.

"It's still possible, but much more difficult."

Delegate Math Determining the ConventionsThere are 42 delegates up for grabs by the Republicans. Candidates have the potential to win all 42 delegates, but would need to win both the statewide vote and all of the state's congressional districts in order to do so.

A Cruz win would mean Trump has an even smaller window to clinch the nomination by the time voting ends in June, increasing the likelihood that Cleveland will be a contested convention.

A Trump win in Wisconsin, particularly one where he wins all 42 delegates, would give him a chance to widen his delegate lead, lowering the percentage he has to win for the nomination, and giving him momentum heading into his home state of New York. Additionally, it could also cement his credibility among unbound delegates who are deciding whom they will support at the convention in July.

Trump's PredictionsTrump has made two different statements today about how he thinks he'll fare Tuesday. At an event in La Crosse, Wisconsin, this morning, he first came out confident, saying he believes they're in for a very, very big victory," before appearing to hedge his bets.

"If we do well here, folks, it's over. If we don't win here, it's not over but wouldn't you like to take the credit?"

One Trump senior adviser told ABC News that their team doesn't expect to win in Wisconsin but does think they will do better than recent polling has suggested.

"It will be tight," one aide said, adding that they "don't think it's a win, though."

The aide says the attendance over the past few days at Trump rallies has fueled the confidence that it won't be a kill shot by Cruz.

Democratic Fight for MomentumFor the Democrats, there are a total of 96 delegates available, 86 of which are pledged and 10 others who are superdelegates: the party leaders or elected officials who can support a candidate of their choosing at any point in the process, including as far out as the Philadelphia convention in July.

"On the Democratic side, it's important because if Bernie Sanders wins [Wisconsin], he's won six out of the last seven states," Dowd said.

"I don't think Hillary loses the nomination because of a loss in Wisconsin, but it complicates her life greatly. ... It continues his momentum and it forces her to rely on superdelegates."