It's the last big test until April 19, and each candidate has a lot to win — or lose.
Trump is coming off the worst week of his 2016 race
. His campaign manager was charged with battery
. He stepped into two controversies over abortion
in three days, both forcing him to issue rare reversals. And he lost state-level fights over delegates
to Cruz in North Dakota, Tennessee and Colorado.
Wisconsin is the first electoral test of whether he's paying a price.
Trump's campaign says it's expecting a close race in Wisconsin
. It's "a toss-up," senior adviser Barry Bennett told CNN.
But the polls show Cruz with a 10-point lead in Wisconsin -- and if that margin grows Tuesday, it'd be a sign that the controversies swirling around Trump's campaign are taking their toll.
Still, Trump was inflating expectations Monday in La Crosse.
"I really believe tomorrow were going to have a very, very big victory. Very very big," he said. "You know, I've been up here a lot. And I love it, and the people I love."
If Cruz wins, it would make Trump's path to 1,237 delegates
before the Republican National Convention precarious. In a tight three-way race, he has little room for error, even with east coast states Trump should win up next. It's made more complicated by Cruz's mastery of the intricate rules and details of the nominating process -- which has left Trump crying foul and threatening lawsuits
in states like Louisiana, where Cruz netted 10 more delegates than Trump even though Trump won the state.
"His team doesn't understand how these processes work so any time they lose they scream, 'The election's been stolen from us,'" Cruz said Monday on WISN radio in Wisconsin. "It's just silliness."
A must-win for Cruz
A loss would dent Trump. But it would crush Cruz, who has retail politicked his way across the Badger State as if it were Iowa in recent weeks.
While Trump is trying to claim a national movement, Cruz is waging a state-by-state, delegate-by-delegate knife fight
to keep Trump from clinching the GOP nomination.
He'll try to pick up 42 more in Wisconsin: 18 that go to the statewide winner, plus 24 more chosen three apiece by the state's eight congressional districts.
Wisconsin is also a test of the strength of the anti-Trump movement
that Cruz is trying to lead. And it willl gauge whether popular, high-level endorsements from the likes of Wisconsin Gov. Scott Walker
or former Florida Gov. Jeb Bush
help push Cruz over the top.
Part of Wisconsin's importance to Cruz is that the calendar soon shifts to shakier ground for him. He's favored in the winner-take-all South Dakota, Montana and Nebraska contests, but could lose big in the next contest on the calendar, New York on April 19, and then Maryland, Pennsylvania, Connecticut, Rhode Island and Delaware the following week.
"Just a couple of weeks ago, all of the media commentators were saying Wisconsin was a state that I could not compete and do well," Cruz said Monday in Kenosha. "They were saying it was a state that was a natural state for Donald Trump. The state historically has been a purple or even a blue state at times. It's a state that is, that is very heavily based on manufacturing, that has a lot of union members and working class members. Supposedly, it was Donald Trump's sweet spot, and yet I think 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."
Can Sanders claim momentum?
He was swept in the South, and bloodied in the Rust Belt. But when the race shifted West, Bernie Sanders won five out of six states, regaining his footing and bolstering his argument to take the race all the way through the last contests on June 7.
A win in Wisconsin would give him a significant boost just as the race heads to New York -- the state where he was born, and which Clinton represented in the Senate. It would also give him victories in six out of the seven states in the month leading up to it -- helping to fuel the passion and small-dollar donations driving his candidacy.
Win or lose, Sanders' path to the Democratic nomination is a tight one
. The party awards its delegates on a proportional basis, so there are no must-win states where he can place big bets the way Republicans have. He'll have to win on the coasts -- and that includes New York and its surrounding territory.
At a rowdy Monday evening rally in Milwaukee, Sanders talked repeatedly about "momentum" -- touting poll results, his growth from 2015 and a string of recent victories.
"Tomorrow, if there is a good turnout here in Wisconsin, if there is a record-breaking turnout here in Wisconsin, we are going to win here as well," he said.
How problematic is a loss for Clinton?
Clinton's campaign has downplayed the Wisconsin primary for weeks, arguing that the state's results won't tip the delegate count significantly in either direction. The former secretary of state wasn't even in Wisconsin on Monday -- instead campaigning in New York, where she faces a closer-than-expected contest in two weeks.
Obviously Clinton would be delighted with a win, but no matter what, she will leave Wisconsin with a clear delegate lead. But, like Michigan in early March, the state could also leave her with a tougher-than-expected primary
on her hands and in a position to explain to backers why she can't put the self-described democratic socialist away.
For more than a month, Clinton has tried to shift her attention to Republicans and the general election. Yet much like Clinton against then-Sen. Barack Obama in 2008, Sanders' persistent presence won't allow it.
Clinton campaign manager Robby Mook is telling supporters not to worry.
In a memo posted on Medium Monday evening, Mook wrote: "Sanders has to win the four remaining delegate-rich primaries -- New York, Pennsylvania, California, and New Jersey -- with roughly 60% of the vote. To put that in perspective: Sanders has thus far won only two primaries with that margin: Vermont and New Hampshire."
He calls the campaign's delegate lead "nearly insurmountable."
Kasich vs. the two-man race narrative
Ohio Gov. John Kasich
has still won only a single state -- his own.
And he's increasingly under pressure from both Trump and Cruz, who are angling behind the scenes for GOP convention rules that would keep him off the first ballot there
, and publicly for him to depart the race.
"He ought to get the hell out, honestly," Trump said Monday in La Crosse. He compared Kasich to Jeb Bush
, Florida Sen. Marco Rubio
and Kentucky Sen. Rand Paul
-- "every single candidate that went out and worked hard, that frankly, in most cases, have done much better than Kasich."
Rubio, in fact, still has more delegates than Kasich.
"He's just a stubborn guy," Trump said of Kasich. "He's stubborn. He doesn't want to leave."
Wisconsin, just like Michigan and Illinois before it, is the sort of state where Kasich ought to have a strong showing. Public polls have showed him within striking distance of Trump for second place -- and finishing ahead of Trump would be a major boost.