Donald Trump and Ted Cruz make final pitches to Wisconsin voters
Donald Trump and Ted Cruz have made spirited final pitches to Wisconsin voters, who will cast ballots in a Republican primary that both consider a key step in the race for president.
After Tuesday, there is a two-week lull before the next important voting, in New York.
Mr Trump is facing pressure on multiple fronts following a difficult week marked by his controversial comments, reversals and rare moments of contrition.
While his past remarks on topics like Mexican immigrants have drawn a backlash, even he appeared to recognise the damage caused by a series of missteps in the lead-up to Wisconsin.
Those included re-tweeting an unflattering photo of Mr Cruz's wife and a series of contradictory comments on abortion that managed to draw condemnation from both abortion rights activists and opponents.
While Mr Trump is the only Republican with a realistic path to clinching the nomination ahead of the Republican convention, a big loss in Wisconsin would greatly reduce his chances of reaching the needed 1,237 delegates before then. A big win for Mr Trump would give him more room for error.
In US primaries voters in each state select delegates pledged to candidates who then vote at the parties' national conventions over the summer.
Mr Trump is facing pressure on two fronts.
In Wisconsin, he has been battered by negative ads. The state's top Republican advertiser has been Our Principles PAC, which pumped almost 1.3 million US dollars into anti-Trump ads. The Club for Growth, which has endorsed Mr Cruz, is spending 800,000 dollars on ads that promote voting for Mr Cruz - not John Kasich - as the best way to ensure a defeat for Mr Trump.
Also, the state's Republican establishment, including governor Scott Walker and some of its most influential conservative talk radio hosts, have lined up to support Mr Cruz.
At the same time, Mr Trump's campaign has been outmanoeuvred by Mr Cruz in some early states where the campaigns are working to ensure that the delegates who attend the convention this summer are loyal to them.
Mr Trump acknowledged his frustrations on US broadcaster CBS in discussing a meeting with members of the Republican National Committee.
"And I did look at my people. I said, 'Well, wait a minute, folks. You know, we should've maybe done better,'" he said. "Except I also said, 'I won the state.' And I think there's a real legal consequence to winning a state and not getting as many delegates."
Meanwhile, Mr Cruz predicted a "terrific victory" during the taping of a town hall interview in Madison that was to be broadcast on Fox News. Mr Cruz also discounted any possibility of someone other than Mr Trump or himself winning the nomination.
"This fevered pipe dream of Washington that at the convention they will parachute in some white knight who will save the Washington establishment, it is nothing less than a pipe dream," he told reporters. "It ain't going to happen. If it did, the people would quite rightly revolt."
On Monday, the Democratic rivals appealed to union members and showed their next-primary hopes by their locations: Bernie Sanders in Wisconsin, where polls show him ahead, and Hillary Clinton in New York, which votes in two weeks and is a must-win state for her.