Ted Cruz wasn't supposed to be the GOP's only hope of stopping Donald Trump, and no one thought he would make his last stand in Wisconsin. But here we are.

MADISON, Wis. — One big difference between a Donald Trump rally and a Ted Cruz rally is that you’re not likely to hear the Constitution mentioned at a Trump event, but Cruz supporters cheer every time their candidate invokes the Constitution, which he does often.

At a rally Sunday night in west-central Wisconsin, Sen. Mike Lee, who is traveling with the campaign, introduced Cruz by telling the crowd he was the only candidate who “understands that restoring and reinvigorating the middle class starts with restoring and reinvigorating the U.S. Constitution.” The audience cheered.

When Cruz took the stage, he said, “Mike Lee is the most serious constitutional scholar to serve in the Senate since the days of Daniel Webster. And I gotta say, Mike Lee would look awfully good in a robe.” More cheers.

It’s telling that Cruz would invoke “the days of Daniel Webster.” Those were the 1840s and ‘50s, when divisions over slavery were opening up cracks in America’s democratic system that would eventually divide the country and plunge it into civil war. Webster, a congressman and secretary of State, was also a key supporter of the Compromise of 1850 and one of the last Whigs to run for president before the party’s dissolution over the question of slavery. Two years after Webster’s death in 1852, the Republican Party formed from a coalition of anti-slavery activists and ex-Whigs.

A Deeply Divided GOP

Today, the Republican Party faces a similar crisis as the GOP primary drags on, pitting Trump supporters against both conservatives and libertarian-minded Republicans, whose rallying cry ahead of Wisconsin’s primary is, simply, #NeverTrump. Some GOP stalwarts have suggested that a Trump nomination would split the Republican Party and trigger a third-party run, perhaps from a newly-formed “conservative” or “federalist” party.

Cruz says only two names should be on the ballot at a contested convention: his and Trump’s.

Cruz doesn’t want that to happen. Before a televised town hall meeting in Madison on Monday, he told reporters his plan to deny Trump the nomination is to “beat him at the ballot box.” Based on the numbers, that’s almost certainly not going to happen. Cruz would need to win 86 percent of the remaining delegates to reach the 1,237 needed to win the nomination on the first ballot at the convention in July.

His backup plan is a so-called “contested convention,” in which the nomination process goes beyond the first ballot. Multiple ballots, though, open up the possibility that someone might be nominated who didn’t run in any of the primaries, like Paul Ryan or Mitt Romney, which is presumably what the Republican Party establishment would prefer.

But Cruz argues there should only be two names on any ballot at a contested convention: his and Trump’s. “It’s a fevered pipe dream of Washington that they can parachute in a candidate,” he said Monday. “It ain’t gonna happen. The voters would rightly revolt.” That’s something short of Trump’s comment that his supporters might riot if he is denied the nomination, but Cruz has a point. Nominating a non-candidate would confirm Republican voters’ worst assumptions about their party’s leadership, especially in a primary season marked by record GOP turnout.

Cruz Was An Unlikely Favorite In Wisconsin

Last year, no one thought Cruz would make his stand in Wisconsin, or that he would even be competitive here. Even after Gov. Scott Walker dropped out last fall, most statewide polls showed Trump and Sen. Marco Rubio as the favorites. Support for Rubio reflected the more moderate temperament of Wisconsin GOP voters, who seemed unlikely to break for Cruz as long as the senator from Florida stayed in the race.

Cruz benefits from the uncanny sophistication of Wisconsin voters.

Even as candidates fell away after Iowa and New Hampshire, it didn’t initially help Cruz in Wisconsin. A Marquette Law School poll in late February showed Trump ahead of Cruz by 11 points, 30 to 19, with Rubio in second place, at 20 percent. After Rubio lost Florida to Trump by double digits and dropped out on March 15, Rubio supporters in Wisconsin had nowhere left to turn but Cruz. Even at Cruz rallies this week, it’s common to hear voters say their first choice was Walker, then Rubio, but now they just want to stop Trump, so they’re voting for Cruz.

But Cruz also benefits from the uncanny sophistication of Wisconsin voters. The political battles fought in this state over the last six years have sharpened and educated the electorate. Every person I’ve spoken to said they voted in the 2012 recall election of Gov. Scott Walker, which he won handily. Statewide turnout for that vote was nearly 58 percent, the highest for a gubernatorial election outside a presidential election year in state history.

Voter Sophistication Plays to Cruz’s Strengths

All that means candidates here have a higher bar to clear than they do in other states. Rhonda Cook, a Cruz supporter who owns a large dairy farm with her husband in Fort Atkinson (between Madison and Milwaukee), told me that Wisconsinites “have a refined ear for b.s.” thanks to the recall election and the fights over Walker’s labor reforms in 2011. For voters like her, Trump’s outrageous rhetoric and vague policy positions “don’t cut it.”

Unlike Trump, Cruz has the policy chops that Wisconsin Republicans are drawn to—and he knows it.

Of course, no one would accuse Cruz of being too subdued in his rhetoric, but unlike Trump he has the policy chops that Wisconsin Republicans are drawn to—and he knows it. That’s why his stump speech includes lines like, “It’s easy to say, ‘Make America Great Again.’ You can print that on a baseball cap. But do you understand the principles and values that made America great in the first place?”

It’s also why Cruz has drawn a crucial endorsement from Walker, who has been been making campaign appearances with Cruz alongside Lee and Carly Fiorina over the past week. Cruz has also secured endorsements from popular conservative talk radio hosts in the state like Charlie Sykes and Vicki McKenna, and won the backing of Wisconsin Rep. Reid Ribble, a moderate who had been struggling to choose between Cruz and Gov. John Kasich up until Saturday afternoon. Monday night, the Cruz campaign announced endorsements from more than a dozen other Wisconsin legislators and more than one hundred county chairs.

Cruz is also likely to benefit Tuesday from Trump’s many missteps this week, most notably his remarks that women should face “some sort of punishment” if abortion were outlawed. During a town hall interview with Megyn Kelly of Fox News on Monday, Cruz said that Trump showed “he’s not serious on this issue or any other issue. Moms are victims of abortion, too.”

Then Cruz delivered a line that might end up defining the Wisconsin contest, and perhaps the entire GOP primary: “These comments are the comments of a liberal who is saying what he thinks conservatives want to hear.”