MILWAUKEE -- Sen. Bernie Sanders won Wisconsin's primary Tuesday, bolstering his case that he remains a powerful force in the Democratic presidential race even as Hillary Clinton's campaign argues she has all but locked up the nomination.
Shortly after polls closed, with exit survey results indicating that he would win, Sanders sent a fundraising appeal to supporters declaring that he had prevailed. With about half the state's vote counted, he was leading Clinton, 55 percent-45 percent.
The exit poll conducted for the Associated Press and the major television networks showed his victory was powered by strong support among men, voters younger than 45, self-identified liberals and independents.
In a victory speech before a crowd of supporters in Wyoming, a state that holds its caucuses on Saturday, Sanders said the win gave him "momentum" going into the contests in New York, Pennsylvania and other eastern states that vote later this month.
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"With our victory tonight in Wisconsin, we have now won seven out of eight of the last caucuses and primaries," Sanders said. "And we have won almost all of them with overwhelming landslide numbers."
Clinton's loss here, even though it has been anticipated for weeks, will raise fresh questions about her vulnerabilities and heighten the stakes for the New York primary this month. The Sanders campaign is pouring considerable resources into New York in the hopes of tripping up Clinton in her adopted home.
Wisconsin's relative lack of diversity also worked to the advantage of Sanders, the exit poll indicated, as the Vermont senator performed much better with white voters than with blacks and Latinos, who have propelled Clinton to her lead nationally.
The primary comes as the candidates have become increasingly combative. Clinton, who has wavered throughout the campaign between engaging Sanders and looking past him toward the general election, has taken a particularly confrontational approach lately.
In recent days, she has accused the Sanders campaign of lying about her support from fossil fuel interests and scolded Sanders protesters who disrupted a rally near her hometown.
She also accused Sanders of being cavalier about Donald Trump's suggestion that women should be punished if they undergo an abortion. Sanders, who supports abortion rights, had complained in a television interview that the news media was paying too much attention to Trump's comments on the subject.
Her sharpened tone reflects annoyance within the Clinton campaign at the Sanders operation. Clinton's advisers resent attacks the Vermonter continues to make on the front-runner's ties to Wall Street and other industries. They argue that the attacks are misleading and that Sanders is so far behind in the race that his criticisms serve only to help the eventual GOP nominee.
Yet Sanders continues to run as if the nomination were in striking distance.
"If we win here tomorrow, it will be a major step forward," Sanders said Monday night in Milwaukee. "The media and all of the pundits considered us a fringe candidacy. After all, they said, who in America is prepared to wage a political revolution? Many millions of Americans are prepared to do just that."
Some Sanders voters said Tuesday that whether or not he could win the nomination was irrelevant to them: They would be voting for him anyway.
"It's a message to Hillary," said Sue Peterson of Milwaukee, a 64-year-old retired factory worker. "Instead of her being angry with Bernie supporters, she needs to listen to what we're saying."
Other Sanders supporters expressed optimism that Sanders would perform an electoral miracle.
"I know they keep saying he doesn't have a chance, but I think he still has a chance," said Kate Mau, 38, the owner of a yarn store interviewed outside a polling station in a middle-class neighborhood south of downtown Milwaukee.
Like several other voters, Mau expressed skepticism about Clinton.
"With Clinton, you're never quite sure if she's being forthright," she said.
Plenty of Sanders supporters in Wisconsin also said they would be just fine voting for Clinton if she wins the nomination - a sentiment that polls indicate is shared by a large majority of Sanders backers nationally. Some even saw good in the Clinton "establishment" roots that Sanders constantly rails against.
"She knows how to pull all the levers in Washington, and that's useful," said Adam Cohen, a 34-year-old engineer who voted for Sanders.
As Sanders moved aggressively to shore up his support in Wisconsin in recent days, Clinton was barely present in the state. Her campaign made a strategic decision to focus instead on New York, where many more delegates are at stake and where a loss would truly damage Clinton's campaign.
Regardless of Sanders' win in Wisconsin, a strong showing for Clinton in New York and then in Pennsylvania, which votes April 26, would practically cement the nomination for her because of the number of delegates each state awards.
Sanders, though, will be a force to contend with in each of those states. He had a huge fundraising month in March. His $44-million haul, which far exceeded that of the Clinton campaign and came from almost entirely small donors, provides him with the money needed to be a constant presence in the costly New York media market.
"I think we have a chance, an excellent chance, to win in New York," Sanders said Tuesday on MSNBC.
The Clinton campaign, anticipating a difficult night on Tuesday, has been maneuvering to put the race in broader perspective. Campaign manager Robby Mook on Monday provided supporters a "facts on where the race stands" posting on Medium. It notes that to catch Clinton, Sanders would have to win primaries by a landslide -- 20-point victories--in New York, California, Pennsylvania and New Jersey, all places where he trails.
"We know the misleading spin will continue," Mook wrote. "But we want you to know the facts about the real state of the Democratic primary."