Donald Trump suffers blow from Ted Cruz in Wisconsin

US Republican Ted Cruz has won the presidential primary in Wisconsin, dealing a blow to front-runner Donald Trump, while Democratic contender Senator Bernie Sanders defeated Hillary Clinton in a close contest.

The loss is more damaging to Trump, because he is in greater danger of failing to lock up the party's nomination ahead of the July convention.

In the Republican race, the first results showed a massive lead for Cruz: With more than 20 percent of votes in, he led Trump by more than 20 percentage points.

Trump may still get some delegates from Wisconsin, however, the state awards some delegates by congressional districts, and he was leading in rural districts in Wisconsin's northwest, according to Washington Post.

Cruz savoured the victory, casting it as proof that the GOP race had turned. The party's anti-Trump forces had coalesced behind an unlikely champion: a Texas senator who seemed like the worst possible choice for the GOP establishment, right up until they met candidate Trump.

Early results with 23 percent of all votes counted show Cruz won 52 percent compared to Donald Trump's 30 percent, while in the Democratic field, Sanders beat Hillary Clinton with 54 percent to 46 percent with 27 percent votes counted, Xinhua reported.

Mathematically, the victories of Cruz and Sanders in Wisconsin did not change the contour of the races where Trump and Clinton continued to hold an almost insurmountable delegate lead.

Trump entered the contest on Tuesday with 736 delegates, 267 delegates more than Cruz, while Clinton led Sanders by 263 pledged delegates, according to the latest delegate count by the New York Times.

However, the victories on Tuesday would be crucial for Cruz and Sanders to build momentum as the contests now move to New York, the home turf for both Trump and Clinton.

"Tonight is a turning point. It is a rallying cry," Cruz told supporters in Milwaukee.

"We have a choice. A real choice. The national political terrain began to change two weeks ago," he said, meaning when he won by a large margin in Utah. Cruz said his campaign had raised $2 million on Tuesday alone.

In the Democratic race, Sanders was leading Clinton by about seven percentage points, 53 percent to 46 percent, with 30 percent of precincts reporting

A victory on that scale may not allow him to make up significant ground on Clinton in the race for Democratic convention delegates. But it will allow Sanders to cite growing momentum going into a crucial contest in New York, where Sanders was born -- and where Clinton served as senator -- on April 19.

A win in Wisconsin also allows Sanders to make the case to "super-delegates", who can make up their minds about whom to support.

After Wisconsin, the next state to vote in the primaries to elect the Republican and Democratic candidates for the November presidential election is New York, where voters will go the polls on April 19.

New York has a large number of both Republican and Democrat delegates at stake.