He will also get a solid boost heading into the delegate-rich New York primary on April 19.

Sanders told a Wyoming audience on Tuesday night that he thinks his recent momentum could translate into more superdelegates, who are free to support whichever candidate regardless of who wins their state, flocking to his campaign. "I think a lot of these superdelegates are going to be saying which candidate has the momentum, which one brings out huge numbers," Sanders said.

Clinton, who was at a New York fundraiser on Tuesday night, tweeted congratulations to Sanders.

Congrats to @BernieSanders on winning Wisconsin. To all the voters and volunteers who poured your hearts into this campaign: Forward! -H — Hillary Clinton (@HillaryClinton) April 6, 2016

ADVERTISEMENT

Heading into Tuesday's contest, polls showed Sanders ahead by a slim margin. And one of the state's top pollsters, Charles Franklin, who runs the Marquette Law School poll, projected Sanders to win by 4 percentage points.

The Badger State has an electorate seemingly designed for Sanders. It is heavily white and tends to favor the more liberal candidate in Democratic primaries.

Tuesday night's win will also help the Sanders campaign rally its supporters and continue its formidable small-dollar fundraising that yielded a record $44 million in March, significantly outraising Clinton.

It was also important for Sanders to win in a primary — not a caucus — as he was developing a reputation for being a candidate who was better off appealing to narrower, more enthusiastic, caucus electorates.

Democratic strategists interviewed by The Hill before the primary said Sanders needed to win by a significant margin in Wisconsin to prove that he is still a viable chance to win the nomination.

"Winning anything close from here on in is not a win for him," Democratic strategist Joe Trippi said of Sanders on the eve of the Wisconsin primary.