U.S. presidential primaries spark back to life Tuesday after an eventful 10-day break with clear frontrunners Donald Trump and Hillary Clinton both facing the real possibility of losing in Wisconsin. Defeat in the north-central state isn't likely to immediately change the course of the overall nominating contest, but it could serve as an indicator of the race's current status ahead of the New York primary on April 19, where polls show both in the lead. It's been a bumpy period for Trump, the Republican billionaire from New York. Although his campaign has seemed bulletproof up until now, his latest controversies, including abortion, opponent Ted Cruz's wife and a journalist who said she was roughed up by Trump's campaign manager, have alienated women voters further, polls indicate. His divisive style is also under scrutiny, and the real estate magnate had a surprise meeting with Republican party chief Reince Priebus in Washington on Thursday amid rumblings that the party would fracture if he were to win the nomination. With polls for the Wisconsin Republican primary showing the ultraconservative Cruz holding a 10-point lead, Trump has launched a series of events in the heartland state to rally support. Moderate John Kasich, the Ohio governor, is polling third and last. Campaigning in Wisconsin on Saturday accompanied by Sarah Palin, Trump attacked Cruz for failing to report a loan from Goldman Sachs, his wife's employer. "They want me to act presidential, they don't want me to call him Lyin' Ted, okay? Lyin' Ted," he told supporters in Racine, to cheers. "No, my wife actually said: No, you're with Sarah today, you have to act very presidential."

The winner of Tuesday's Republican primary will take most of the 42 delegates on offer. If Cruz wins, he will certainly claim it as a turning point in the race, but mathematically speaking he will struggle to overcome his overall delegate deficit. Currently, Trump has 739, Cruz 460 and Kasich 145. To win the Republican nomination outright, a candidate needs 1,237. In North Dakota, Republican activists gather this weekend at a state convention to select 25 of the state's 28 delegates, but unlike those from most other states, they won't be bound to a particular candidate at the party's convention in July. The other three are RNC members who are automatic delegates.

For Clinton, a loss in Wisconsin would be more symbolic than anything else, as the state distributes delegates proportionally according to the primary results. But she comes into the contest having lost five of the last six states to Bernie Sanders, and polls show him finishing on top in Wisconsin. The Vermont senator has already notched victories in two neighboring states, Minnesota and Michigan, and his popularity is undeniable in Wisconsin cities like Madison, which have a high concentration of university students. Sanders, who has energized young Democrats, is trying to dispel the notion that Clinton is a better candidate for defeating Trump in the general election in November. "In the last national CNN poll we beat Trump by 20 points and that's before we really begin to expose what a nutcase he really is," Sanders told supporters Friday in Sheboygan. With the momentum in Sanders' camp, tensions are starting to rise between him and Clinton.

The former U.S. top diplomat showed a rare flash of anger on Thursday when a Greenpeace activist asked her if she would reject campaign contributions linked to the oil and gas industries. Clinton, who was shaking hands along a rope line, responded sharply: "I am so sick, I am so sick of the Sanders campaign lying about me, I'm sick of it," jabbing her finger at the young woman in a video that went viral. While Clinton acknowledged receiving donations from people who work for such companies, the oil and gas companies themselves are not permitted to contribute to candidates. Spotting an opening, Sanders said in Eau Claire, another Wisconsin city, on Saturday: "When you have a handful of billionaires trying to buy elections, that's not called democracy, that's called oligarchy." Despite his recent successes Sanders is still trailing in the race for delegates. Clinton has 1,259 compared to his 1,020, according to a CNN tally. The former first lady benefits from the critical support of nearly 500 "super delegates," elected officials and Democratic Party leaders who cast votes at the party's convention in July. To win the Democratic nomination, a candidate needs 2,383 delegates.

Meanwhile, Trump on Saturday again accused U.S. allies of not pulling their weight in the NATO military alliance, despite a call from President Barack Obama to tone down his foreign policy rhetoric. The billionaire businessman told a campaign rally in Racine, Wisconsin that allies in the North Atlantic Treaty Organization "are not paying their fair share" and called the 28-nation alliance "obsolete." "Either they pay up, including for past deficiencies, or they have to get out. And if it breaks up NATO, it breaks up NATO," Trump said. Trump has frequently criticized NATO in recent weeks as the race for the Republican nomination for the Nov. 8 election has heated up. On Friday, Obama cast doubt on Trump's fitness for office after the former reality TV star refused to rule out using nuclear weapons in Europe and said that Japan and South Korea might need nuclear arms. "The person who made the statements doesn't know much about foreign policy or nuclear policy or the Korean peninsula, or the world generally," Obama said, warning that the world is closely watching the U.S. election rhetoric. "I've said before that people pay attention to American elections. What we do is really important to the rest of the world," Obama said. Trump's comments on NATO have also sent ripples through the Republican Party, which has traditionally promoted a muscular foreign policy.

Trump also predicted that the United States is on course for a "very massive recession," warning that a combination of high unemployment and an overvalued stock market had set the stage for another economic slump. "I think we're sitting on an economic bubble. A financial bubble," the billionaire businessman said in an interview with The Washington Post published on Saturday. The former reality TV star said that the real U.S. jobless figure is much higher than five percent number released by the U.S. Bureau of Labor Statistics. "We're not at 5 percent unemployment," Trump said. "We're at a number that's probably into the twenties if you look at the real number," he said, adding that the official jobless figure is "statistically devised to make politicians, and in particular presidents, look good." Trump said "it's a terrible time right now" to invest in the stock market, offering a more bleak view of the U.S. economy than that held by many mainstream economists.