The event comes one week before the state's April 5 primary, a critical test of the candidates' strength before the campaign heads to eastern states later in the month.

Here are five things to watch:

Cruz and Trump get negative

Even the bit about the size of Trump's manhood didn't go quite this far.

Trump and Cruz are in the midst of the campaign's most bitter, personal fight. It started when Trump blamed Cruz for an unaffiliated super PAC's ad featuring a nearly naked Melania Trump, without any evidence that Cruz was behind it. Then Trump attacked Heidi Cruz.

It's gotten bad enough that Cruz wouldn't say in an interview with CNN's Sunlen Serfaty on Monday whether he'll still back Trump if he wins the Republican nomination.

JUST WATCHED Ted Cruz: Trump threatened my wife Replay More Videos ... MUST WATCH Ted Cruz: Trump threatened my wife 01:05

"I'm not in the habit of supporting people who attack my wife and attack my family," Cruz said. "Donald Trump is not gonna be the nominee. We are gonna beat him for this nomination."

Trump, meanwhile, has threatened lawsuits over the Cruz campaign's success in picking up 10 extra delegates in Louisiana, even though Trump actually won the state.

And the two are at each other's throats over who leaked what pieces of information in negative stories about the other.

Cruz challenged Trump to debate at CNN's town hall during a Monday campaign stop in Rothschild.

"Donald, why don't you show up and debate like a man? I recognize that Donald prefers to communicate in 140 characters or less ," Cruz said.

Though they won't be on stage together, the fight between Trump and Cruz will be Tuesday night's main attraction.

The Lewandowski factor

Trump heads into Tuesday's town hall after a dramatic day on the campaign trail. His campaign manager, Corey Lewandowski, was arrested and charged with misdemeanor battery on Tuesday morning, with Florida police releasing video showing him grabbing former Breitbart reporter Michelle Fields by the arm and pulling her backwards.

But Trump stood by his man.

On Twitter, Trump suggested that Fields had actually been trying to grab him.

He also accused Fields of changing her story. And, aboard his plane in Wisconsin later on Tuesday, Trump told reporters that he doesn't know that Fields' bruises, which she showed the police, were a result of Lewandowski's grab.

"Wouldn't you think she would have yelled out a scream if she had bruises on her arm?" Trump said.

Trump's foes also weighed in on the news.

Cruz said the incident reflects within Trump's campaign an "abusive culture, when you have a campaign that is built on personal insults, attacks and now physical violence."

Kasich made the Trump campaign's treatment of women personal, saying Fields "could have been one of my daughters," and that he'd either suspend or fire the aide if a similar incident happened on his campaign.

The Lewandowski arrest dominated Tuesday's news, and isn't likely to disappear anytime soon.

Trump on policy

Cruz's go-to line of attack on Trump has been to question his conservatism -- and his consistency on policy.

Increasingly, as Trump nears the general election, his policy positions are coming under scrutiny. His comments in editorial board meetings with The Washington Post and The New York Times both made waves.

JUST WATCHED Ted Cruz challenges Donald Trump to one-on-one debate Replay More Videos ... MUST WATCH Ted Cruz challenges Donald Trump to one-on-one debate 00:45

When The Post asked if Trump would consider the use of strategic nuclear weapons against ISIS, he said he's a "counter-puncher," and pointed to his campaign trail exploits against people like Jeb Bush.

It's a central challenge for a man who is new to politics: talking fluently about policies he hasn't had to address in his work life before he decided to run for president.

Those moments will be closely watched -- not just for instant impact, but for what they could mean in the general election.

Will Kasich hit anybody?

The subject line on John Kasich's fundraising email Monday afternoon was an eyebrow-raiser: "Off Limits."

He was talking about families, and declared that "enough is enough with the mud slinging and the personal attacks."

Photos: Can you guess the 2016 contenders' campaign logos? Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 1 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 2 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Former Gov. Jeb Bush, R-Florida Hide Caption 3 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 4 of 41 Photos: Can you guess the 2016 contenders' campaign logos? U.S. Sen. Marco Rubio, R-Florida Hide Caption 5 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 6 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Former Secretary of State Hillary Clinton, Democrat Hide Caption 7 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 8 of 41 Photos: Can you guess the 2016 contenders' campaign logos? U.S. Sen. Bernie Sanders, independent from Vermont running for Democratic nomination Hide Caption 9 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 10 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Real estate mogul Donald Trump, Republican Hide Caption 11 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 12 of 41 Photos: Can you guess the 2016 contenders' campaign logos? U.S. Sen. Ted Cruz, R-Texas Hide Caption 13 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 14 of 41 Photos: Can you guess the 2016 contenders' campaign logos? John Kasich, R-Ohio Hide Caption 15 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 16 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Retired neurosurgeon Ben Carson, Republican Hide Caption 17 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 18 of 41 Photos: Can you guess the 2016 contenders' campaign logos? U.S. Sen. Rand Paul, R-Kentucky, who has dropped out of the presidential race. Hide Caption 19 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 20 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Former U.S. Sen. Rick Santorum, R-Pennsylvania, who has dropped out of the presidential race. Hide Caption 21 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 22 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Former Gov. Rick Perry, R-Texas, who has dropped out of the presidential race. Hide Caption 23 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 24 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Former Gov. George Pataki, R-New York, who has dropped out of the presidential race. Hide Caption 25 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 26 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Former Gov. Mike Huckabee, R-Arkansas, who has dropped out of the presidential race. Hide Caption 27 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 28 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Former Gov. Martin O'Malley, D-Maryland, who has dropped out of the presidential race. Hide Caption 29 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 30 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Former Hewlett-Packard CEO Carly Fiorina, Republican, who has dropped out of the presidential race. Hide Caption 31 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 32 of 41 Photos: Can you guess the 2016 contenders' campaign logos? U.S. Sen. Lindsey Graham, R-South Carolina, who has dropped out of the presidential race. Hide Caption 33 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 34 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Former U.S. Sen. Lincoln Chafee, D-Rhode Island, who has dropped out of the presidential race. Hide Caption 35 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 36 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Wisconsin Gov. Scott Walker, Republican, who has dropped out of the presidential race. Hide Caption 37 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 38 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Former U.S. Sen. Jim Webb of Virginia, Republican, who has dropped out of the presidential race Hide Caption 39 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Hide Caption 40 of 41 Photos: Can you guess the 2016 contenders' campaign logos? Louisiana Gov. Bobby Jindal, Republican, who has dropped out of the presidential race Hide Caption 41 of 41

The Ohio governor has won some supporters through his above-the-fray approach. But he has also found himself being shuffled to the side -- urged not to even compete in some states -- by anti-Trump Republicans who fear he'll hurt Cruz's chances of winning and therefore deny Trump the delegates he needs to clinch the nomination.

So he has some decisions to make. Will Kasich put his foot down and go after one, or both, of his opponents for the direction they've taken the race and tell voters it's disqualifying?

How he handles the clash between Trump and Cruz could set the tone for Kasich's next three weeks, since Wisconsin is the only major contest before New York's April 19 primary.

The Scott Walker effect

When he launched his short-lived 2016 presidential campaign, Wisconsin Gov. Scott Walker was supposed to be the perfect blend of a competent, credentialed executive and a rock-ribbed conservative outsider unstained by Washington. His biggest rival was thought to be Cruz.

Then Trump ruined all of that.

The real-estate mogul's distaste for politicians was so strong that Walker, who spent his adult life in local politics, couldn't match it. His argument that he is stronger than everybody else was enough to drown out Walker's case about beating back labor unions.

Walker got a little revenge on Tuesday, when he announced his endorsement of Cruz on a radio show.

The Wisconsin governor could set the tone for a state that's do-or-die for Cruz. Walker could be positioning himself for a future run. At the CPAC gathering near Washington earlier this year, he sought to minimize the damage that anti-Trump Republicans fear he's doing to the conservative brand.

"I want to offer you some enthusiasm, some optimism today, and tell you no matter what's happening there, the conservative movement is alive and well in states all across America," he said there.

And he's thrown out the possibility that if the GOP race is decided at the convention in Cleveland, the nominee might not be one of the three candidates for president right now.

Expectations game

Kasich wasn't exactly raising the stakes in Wisconsin when he talked with reporters Monday in West Salem.

Asked to name one state he can win as the campaign moves forward, he said: "Yeah, I mean we'll see, yeah."

"I'm not going to be predicting because every time I predict it ends with you people coming and throwing my words back in my face. The key for us is to pick up delegates," he said.

So cross Kasich off the list of those whose fate depends on Wisconsin's outcome.

Cruz, on the other hand, has much more on the line. Trump is already on course to come close to winning 1,237 delegates -- enough to clinch the Republican nomination outright. Cruz is within striking distance in the Badger State, and if he's to deny Trump that mark, he can no longer afford to lose winnable states.

Amid all the personal insults, Cruz seems to have recognized this as a moment to strike.