MADISON, Wis. – America's three-ring presidential circus is camped out for the moment in Wisconsin, a state all too familiar with political upheaval and a potential general election battleground in this wild and often surprising race.

The Wisconsin primary on Tuesday lands at a relative lull in the calendar of state presidential contests, leaving ample time for the Republican and Democratic contenders to campaign across Minnesota's eastern neighbor. All five stumped throughout Wisconsin in the past week, flooding the airwaves with commercials and plotting last-minute stops.

"If we win in Wisconsin, it's pretty much over," Republican front-runner Donald Trump, currently trailing in polls here to Texas Sen. Ted Cruz, said last week at a rally in Janesville.

For Republicans trying to derail Trump's candidacy, Wisconsin has emerged as a last-ditch bulwark of their strategy.

It is also the latest front in Democratic front-runner Hillary Clinton's attempts to close down Vermont Sen. Bernie Sanders, and polls show a tight race with a likely split between the state's two largest cities.

"Madison is absolutely home base for a candidate like Sanders, and the city of Milwaukee is made for Hillary Clinton," said Joe Zepecki, a Wisconsin Democratic strategist.

Since first electing Republican Gov. Scott Walker in 2010, Wisconsin has emerged as an emblem of the bitter divisions that now define America's political discourse.

Walker and a Republican-controlled Legislature pushed state policy far to the right of center by drastically curbing union power (triggering massive statehouse protests in response), lowering taxes while cutting state aid for public schools and universities, and enacting strict voter ID laws.

Simultaneously, U.S. Rep. Paul Ryan of Janesville has become a GOP star, first as the party's vice presidential candidate in 2012 and then by taking over as speaker of the House late last year.

"If you look for the center of gravity in national Republican politics the last few years, it's somewhere in Wisconsin," said former Gov. Scott McCallum, a Republican who led the state from 2001 to 2003.

Walker, whose own presidential bid died last September, endorsed Cruz last week. Ryan and Reince Priebus, the Republican National Committee chairman who previously led the Wisconsin GOP, are neutral in the race but find themselves mired in their party establishment's meltdown over Trump.

Republicans are dominating state politics in the Walker era. But they haven't been able to break Wisconsin's habit of swinging back to Democrats in higher-turnout presidential years. Obama won big here both times, and in 2012 the state elected Democrat Tammy Baldwin to the U.S. Senate, making her the country's first openly gay senator.

Wisconsin hasn't gone Republican for president since 1984, and the University of Virginia's Center for Politics rates it "likely Democratic" in the presidential race. But with its large populations of blue-collar workers and seniors, and given the GOP's lock on statewide power, it's likely to be high on the list of possible Republican pickups this year as the two parties battle for the Midwest.

"With states like Virginia and Colorado increasingly going for Democrats for president, Republicans need to look for states to broaden their map and put Democrats on defense and that means places like Wisconsin and Pennsylvania," said Zepecki, who worked for Obama's re-election campaign in Wisconsin. In 2004, Democrat John Kerry beat then-President Bush here by less than one percentage point.

Wisconsin Democrats hope for another presidential wave this year. Republican U.S. Sen. Ron Johnson, elected alongside Walker in 2010, faces a rematch with former Sen. Russ Feingold; polls show a lead for the former three-term Democrat, who still boasts higher name recognition than Johnson.

Walker's job isn't open again until 2018; despite his slumping statewide approval ratings over the last year, Republicans close to the 48-year-old governor believe he's likely to seek a third term. Democrats see little hope of overturning the large Republican majority in the state Assembly, but depending how the presidential race goes they see a shot at undoing the GOP's much slimmer state Senate majority.

"If Democrats do well at the top of the ticket, and particularly if Trump is at the top of the ballot, that could help Democrats win back the state Senate," said Barry Burden, a political-science professor at University of Wisconsin-Madison.

Wisconsin also has a distinct knack for backing the eventual party nominee in its presidential primaries. Since 1968, every Democratic and Republican winner of the Wisconsin primary has gone on to capture the party nomination with just one exception: In 1984, Wisconsinites picked Gary Hart over Minnesotan Walter Mondale in the Democratic primary.

"No state has a better record," Burden said.

It's another incentive for the five presidential candidates. For Trump, a win would defy expectations from several recent polls showing a Cruz lead.

But veteran Wisconsin Republicans said their party faithful, concentrated in the Milwaukee suburbs that fueled Walker's political ascent, are not amenable to Trump. Even as Walker pushed the state to the right, he did it with an understated Midwestern style. A handful of prominent conservative talk radio hosts in Milwaukee, also instrumental in Walker's political career, have been bashing Trump on the air.

"The kind of Republicans we like here are Scott Walker and Paul Ryan who actually offer solutions to problems," said Craig Graul, a GOP strategist based in Green Bay. "In general Trump's shtick isn't well-made for Wisconsin."

Trump's blistering critiques of Walker at his recent Wisconsin stops are probably counterproductive. "He doesn't look like a motorcycle guy," Trump said in Janesville, ridiculing Walker's well-known fondness for Harley-Davidsons.

"The one thing I know for sure is that Wisconsin Republicans are still 100 percent rock solid with Scott Walker, and how anyone who wants to win the Republican vote thinks they can do it by criticizing him is beyond me," Graul said.

Trump supporters at the Janesville rally showed little fidelity to the Republican Party. When Trump mentioned Ryan, in his own hometown, the crowd booed — surprising even Trump himself. "I was told to be nice to Paul Ryan," he said.

Shelby Welchel, a 49-year-old Janesville resident, said she came to see Trump because she's never been to a political rally and, "I wanted to knock something off my bucket list." She had plans to take in a Sanders rally the following day in La Crosse, and said she could see voting for either Trump or Sanders in November.

"These are guys who both speak their mind and don't care who they offend," said Welchel, a former social services caseworker who now volunteers at shelters. "If it was Trump versus Bernie in November, I'd have a tough decision."

A Cruz event the following day at a Sheraton Hotel near downtown Madison seemed specifically designed to exploit Trump's pronounced polling weakness among women, highlighted last week by his remark — later retracted — that if abortion were made illegal women getting them should be punished.

Billed as the rollout of a "Women for Cruz coalition," the event found the candidate along with his wife, Heidi Cruz, his mother, Eleanor Darragh, and former GOP presidential candidate Carly Fiorina sitting in plush, gold-colored easy chairs on a raised platform that resembled a TV talk show set.

"I want to introduce you to three strong women I admire," Cruz said at the start, opening an hourlong discussion that ditched his sharply conservative rhetoric in favor of personal stories and confessional anecdotes.

"I just love Ted Cruz," said Natalie Seib, a 27-year-old stay-at-home mom from Madison who cradled her infant son as she stood against the wall in the packed hotel ballroom. "I appreciate the morality that guides him. He knows what he wants and he sticks to it."

While the five candidates crisscross the state this final weekend before the primary, Wisconsinites have already been voting for two weeks. State law allows in-person absentee voting up to 14 days before the election. At Hudson City Hall on a recent weekday, there was a steady trickle of voters throughout the morning.

Dan Setzer, a Stillwater barber who lives across the river, voted for Trump.

"He talks the way normal people talk," Setzer said. "I know he can be inflammatory but we all have our character faults. The way that he speaks, I believe that he really intends to do the things he talks about."

Kate Langenohl, a stay-at-home mom in Hudson, voted for Clinton and called her the only logical choice among the remaining candidates in both parties.

"She just has so much experience," Langenohl said. "I feel like there's a lot of scary things going on in the country and the world right now, and she's the only one who really knows how this works."

Patrick Condon • 651-925-5049