U.S. primary season: Ted Cruz, Bernie Sanders win in Wisconsin

Republican Donald Trump emerged from Wisconsin as a damaged front-runner following a crushing primary loss to rival Ted Cruz, deepening questions about the billionaire businessman's presidential qualifications and pushing the Republican Party toward a rare contested convention nomination fight.

Democrat Bernie Sanders also scored a sweeping victory Tuesday in Wisconsin's primary that gives him a fresh incentive to keep challenging Hillary Clinton. But Sanders still lags significantly behind Clinton in the all-important delegate count.

Both parties were turning their sights toward New York, which offers a massive delegate prize in its April 19 contests. It marks a homecoming of sorts for several candidates, with Trump, Clinton and Sanders all touting roots in the state.

"Tonight is a turning point," Cruz told cheering supporters at a victory rally. "It is a call from the hardworking people of Wisconsin to America. We have a choice. A real choice."

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Cruz, a Texas senator with a complicated relationship with Republican leaders, also cast his victory as a moment for unity in a party that has been roiled by a contentious primary campaign.

But Trump was unbowed. His campaign put out a biting statement: "Ted Cruz is worse than a puppet - he is a Trojan horse, being used by the party bosses attempting to steal the nomination from Mr. Trump."

Sanders's sweeping win in virtually every county in Wisconsin, except Milwaukee, gives him greater incentive to keep competing against Clinton. But he still trails her in the pledged delegate count and has so far been unable to persuade superdelegates the party officials who can back any candidate to drop their allegiance to the former secretary of state and back his campaign.

At a raucous rally in Wyoming, the site of Democratic caucuses on April 9, Sanders cast his victory as a sign of mounting momentum for his campaign.

"With our victory tonight in Wisconsin, we have now won seven out of eight of the last caucuses and primaries," he declared.

The results in Wisconsin make it likely both parties' primaries will continue deep into the spring, draping front-runners Trump and Clinton in uncertainty and preventing both from fully setting their sights on the general election.

With an overwhelming white electorate and liberal pockets of voters, Wisconsin was favorable territory for Sanders. In a sign of Clinton's low expectations in the Midwestern state, she spent Tuesday night at a fundraiser with top donors in New York City.

Clinton congratulated Sanders on Twitter and thanked her supporters in Wisconsin. "To all the voters and volunteers who poured your hearts into this campaign: Forward!" she wrote.

Sanders' win will net him a handful of additional delegates, but he'll still lag Clinton significantly. With 86 delegates at stake in Wisconsin, Sanders won at least 45 delegates to Clinton's 31. Ten delegates remain to be allocated, pending final vote tallies.

With most of Wisconsin's delegates allotted, Clinton now has 1,274 delegates to Sanders' 1,025, based on primary and caucus results alone. When including superdelegates, Clinton has a wider lead 1,743 to 1,056. It takes 2,383 delegates to win the nomination.

Sanders must win 67 per cent of the remaining delegates and uncommitted superdelegates to win the nomination.

Trump deals with controversies

While Trump has been the dominant force in the Republican race, he battled a series of campaign controversies in the lead-up to Wisconsin, including his campaign manager's legal problems following an altercation with a female reporter and his own awkward stumbles in clarifying his views on abortion. Wisconsin's Republican establishment, including Gov. Scott Walker, has also campaigned aggressively against the businessman.

Exit polls in the state underscored the concerns about Trump that are surging through some corners of the Republican Party. A majority of Republican voters said they're either concerned or scared of a potential Trump presidency. More than a third said they were scared about what Trump would do as president, and about two in 10 said they were concerned, according to surveys conducted by Edison Research for The Associated Press and television networks.

Cruz has won at least 33 delegates in Wisconsin and Trump will gain at least three. Six delegates are still up for grabs, pending the outcome in two congressional districts.

With Wisconsin results included, Trump led with 740 delegates to Cruz's 514, while Ohio Gov. John Kasich had 143. It takes 1,237 delegates to win the nomination.

Trump still has a narrow path to claim the nomination by the end of the primaries on June 7. But by losing Wisconsin, the real estate mogul has little room for error in upcoming contests. He must win 57 per cent of the remaining delegates to win the nomination before the convention; he has won 46 per cent thus far.

But the result may be more of a victory for the anti-Trump forces than Cruz himself. The next primary is in New York on April 19, with contests in Pennsylvania, Connecticut and Maryland soon after. Cruz's prospects in those states are highly debatable.

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

Both candidates have implored Kasich to leave the race, with a Cruz spokesperson saying Tuesday night the Ohio politician must be angling for a vice presidential entreaty from the winning nominee.

To win a prolonged convention fight, a candidate would need support from the individuals selected as delegates. The process of selecting those delegates is tedious, and will test the mettle of Trump's slim campaign operation. Wisconsin native Paul Ryan, the House Speaker, has been floated as a potential candidate to emerge at a convention.

Cruz prevailed in an early organizational test in North Dakota, scooping up endorsements from delegates who were selected at the party's state convention over the weekend. While all 28 go to the national convention as free agents, 10 said in interviews they were committed to Cruz. None has so far endorsed Trump.

Despite the concern among some Wisconsin Republicans about Trump becoming president, nearly six in 10 GOP voters there said the party should nominate the candidate with the most support in the primaries, which so far would be Trump. Even among voters who favoured Cruz, four in 10 said the candidate with the most support going into the convention should be the party's nominee.