Ted Cruz has easily won the Wisconsin Republican presidential primary, dealing a blow to frontrunner Donald Trump's hopes of accumulating enough delegates for the party's nomination.
Cruz's double-digit win over Trump on Tuesday was a breakthrough for Republican Party forces battling to block Trump, and it raised the prospect of a prolonged nomination fight that could last to the July convention in Cleveland, Ohio.
Bernie Sanders, Democratic presidential contender, also won in Wisconsin, gaining momentum in his fight against frontrunner Hillary Clinton and shrinking her commanding lead in delegates.
Trump entered the night with 737 convention delegates to Cruz's 481, leaving him 500 delegates short of the 1,237 needed to become the party's nominee in the November 8 election.
But Cruz said the party was beginning to rally to his campaign and he was cutting Trump's lead, although he acknowledged the growing possibility that the fight could go all the way to the convention.
"Either before Cleveland, or at the convention in Cleveland, together we will win a majority of the delegates and together we will beat Clinton in November," Cruz told supporters in Milwaukee.
"We're winning because we're uniting the Republican Party."
'Extraordinary voter turnout'
In the Democratic race, the win for Sanders, a US senator from Vermont, is his sixth in the last seven nominating contests.
Sanders said his message of breaking up the big banks, reining in Wall Street and reducing income inequality was bringing new and young voters into the process.
"What we have been seeing throughout this campaign is extraordinary voter turnout in state after state," Sanders said at a rally in Laramie, Wyoming.
Heading into Tuesday, Clinton led Sanders by 263 pledged delegates in the race for the 2,383 needed to be nominated at the party's July convention in Philadelphia.
She also has a big lead in superdelegates, who are party leaders free to back any candidate.
Sanders needs to win up to two-thirds of the remaining delegates to catch up with Clinton, who will keep accumulating delegates even when she loses under a Democratic Party system that awards them proportionally in all states.
Al Jazeera's Kimberly Halkett, reporting from Wisconsin, said that despite the losses, the delegation mass still favoured the frontrunners Trump and Clinton.
"But at the same time, what we've seen is that their momentum has been blunted and the pathway to those nominations just got a lot more messy," she said.
"Meanwhile, Cruz told his supporters he was the one who can unify the Republican Party. He was speaking indirectly at the fact that Trump has gathered an awful lot of negative press recently which could've contributed to the significant loss in this state."
Source: Al Jazeera and agencies