MILWAUKEE — Republican Ted Cruz and Democrat Bernie Sanders hoped to turn the tables on their parties' front-runners in Wisconsin Tuesday and emerge from the Midwestern battleground reinvigorated in their pursuit of the White House.

Even with wins in Wisconsin, Cruz and Sanders would still face tough mathematical odds of winning their parties' nominations before the summer conventions. Still, losses Tuesday for leading contenders Donald Trump and Hillary Clinton would keep an aura of uncertainty hanging over both races.

Sanders has vowed to stay in the Democratic race through all of the voting contests, and the Vermont senator has raised enough money to make good on that pledge. A win in Wisconsin would be a boost for his campaign, but would still leave him trailing Clinton in the delegate count.

It's Republicans who are bracing for a real convention fight, which could occur if Trump can't reach the 1,237 delegates needed to clinch the nomination through the normal voting process. Cruz, the Texas senator who has emerged as Trump's closest rival, was casting Wisconsin as crucial to GOP efforts to stop the billionaire businessman.

"What we are seeing in Wisconsin is the unity of the Republican Party manifesting," Cruz said during one of his final campaign stops.

For Trump, the long lead-up to Wisconsin's contest has included one of the worst stretches of his candidacy. He was embroiled in a spat involving Cruz's wife, which he now says he regrets, was sidetracked by his campaign manager's legal problems after an altercation with a female reporter, and stumbled awkwardly in comments about abortion.

Still, Trump made a spirited final push in the state and predicted a "really, really big victory."

"If we do well here, it's over," he said. "If we don't win here, it's not over."

Complicating the primary landscape for both Cruz and Trump is the continuing candidacy of John Kasich. The Ohio governor's only victory has come in his home state, but he's still picking up delegates that would otherwise help Trump inch closer to the nomination or help Cruz catch up.

Trump has grown increasingly frustrated with the governor and has joined Cruz in calling for Kasich to end his campaign. Kasich cast Trump's focus on him as a sign that he's best positioned to win over the businessman's supporters.

"They're not really his people," Kasich said. "They're Americans who are worried about, they're really most worried about their kids, are their kids going to have a good life?"

If Cruz wins all of Wisconsin's 42 delegates, Trump would need to win 57 percent of those remaining to clinch the GOP nomination before the July convention. So far, Trump has won 48 percent of the delegates awarded.

Paul Lorentz, was in line at 6:30 a.m. in Sun Prairie, Wisconsin, on Tuesday to cast his vote for Kasich. Lorentz said he typically votes Democratic in the general election but Republican in Wisconsin's open primary in order to sway the GOP to a better candidate.

"My hope is always to have two acceptable candidates running for president," he said.

Among Democrats, Clinton has 1,243 delegates to Sanders' 980 based on primaries and caucuses. When including superdelegates, the party officials who can back any candidate, Clinton holds a much wider lead — 1,712 to Sanders' 1,011. It takes 2,383 delegates to win the Democratic nomination.

On the eve of voting in Wisconsin, Clinton's campaign manager argued that Sanders' only path to victory "relies on overturning the will of the voters." In a memo to supporters, Robby Mook wrote that Sanders' strategy now is "a combination of trying to flip pledged delegates at state and county conventions, while also convincing superdelegates that he deserves their support."

Sanders would need to win 67 percent of the remaining delegates and uncommitted superdelegates to catch up to Clinton. So far, he's winning 37 percent.

Even if Sanders wins in Wisconsin, he's unlikely to gain much ground. Because Democrats award delegates proportionally, a narrow victory by either candidate on Tuesday would mean that both Sanders and Clinton would get a similar number of delegates.

Carrie-Ann Todd, a 39-year-old mother saddled with student debt, said she voted for Sanders because of his efforts to address the cost of college.

"I'm paying more on my student loans than I am on my cars," Todd says. "I don't know if he'll get any support if he gets into the White House, but it's worth a shot."

Pace reported from Washington. Associated Press writers Jill Colvin, Jonathan Lemire, Hope Yen, Stephen Ohlemacher, Bryna Godar and Greg Moore contributed to this report.