Bernie Sanders could win in Wisconsin tonight. But what matters is by how much.

Bernie Sanders's fans could have something to celebrate in Wisconsin on Tuesday night, with the Vermont senator poised to potentially win big in the state.

But if their goal is for Sanders to actually win the nomination — as opposed to stringing up symbolic victories over Hillary Clinton — they should wait to see if he can dramatically outperform expectations and take the state by double digits.

Most polls have found Sanders up by anywhere from 2 to 8 points in the state. He will probably need to beat Hillary Clinton by much more than that to have a real shot at genuinely challenging her strong delegate lead in the Democratic contest.

"Sanders needs to start winning by a couple of touchdowns for the media to start taking his narrative seriously," says Michael Wagner, an elections specialist at the University of Wisconsin Madison.

(Pedro Portal/El Nuevo Herald/TNS/Getty Images)

The good news for Sanders fans is there's reason to believe the polls could be underestimating his support in Wisconsin.

The state is heavily white, has a strong network of young voters, and maintains a strong progressive tradition. In 2008, Wisconsin broke for Barack Obama over Clinton by a massive 17-point margin.

Sanders will be looking to replicate that success on Tuesday. But the state is not just a must-win for Sanders — it's a state he needs to win by enough to significantly boost his chances of upsets in the bigger states that lie ahead, like Pennsylvania and New York.

Sanders can't just win in Wisconsin. He needs to win big.

Despite the claims of some Sanders fans, the Democratic race really isn't wide open.

Clinton is up by more than 220 pledged delegates. Sanders's supporters have taken to pointing out that since only about half of the pledged delegates have been decided, there's still enough states remaining for Sanders to still close the gap. (Clinton also leads among superdelegates.)

And that's true. The problem is that of the states remaining, very few are expected to break heavily for Sanders.

"There's a bunch of states after [Wisconsin] that I think will go for Clinton," says Alan Abramowitz, an Emory University political scientist. "My view is people are giving too much importance to Wisconsin: It seems to line up well for Bernie, but I don't think it's going to have any influence on what happens later."

To get a sense of just how difficult it would be for Sanders to close the delegate gap, FiveThirtyEight's Nate Silver came up with a "Bernie miracle" model that lays out a path for him to win the 988 delegates he needs.

Silver found that Sanders would need to win Wisconsin by 16 points to run even with Clinton nationally. He'd also need to win Clinton's home state of New York by at least 4 points, though most polls have found Sanders trailing there.

"I think she would need to lose by 15 points or more in Wisconsin to really worry about the narrative of the popular choice not breaking for her," says Wagner, the University of Wisconsin political scientist.

Why the polls could be underestimating Sanders in Wisconsin

Last week, the student newspaper at the University of Wisconsin published a story advising Sanders's young fans how to throw a "rager" for their favorite candidate. (Recommendations included shouting "Feel the Bern!" when taking a hit from a marijuana blunt, as well as charging $5 a cup for an average American but $1,000 a cup for millionaire and billionaire attendees.)

Sanders's popularity among young voters is one reason close watchers of the race think he could do better today than the polls currently suggest: The state has a strong university system, and there's been excitement building since he drew nearly 10,000 people in Madison last summer with what was then the biggest rally of any campaign.

"The campuses are really crackling with energy related to Sanders," Wagner says. "Sanders has made a huge effort there."

Wisconsin is often compared by election trackers to Michigan, where Sanders won a shocking a victory after trailing in the polls by as much as 30 points. Could the polls be similarly underestimating his strength in Wisconsin?

In addition to strong young youth voter turnout, here are a few other reasons to believe Sanders will outperform the polls today:

1) Sanders has been able to invest heavily in Wisconsin, building a voter mobilization campaign infrastructure and far outpacing Clinton's advertising spending in the state. (RealClearPolitics reports Sanders has run 1,000 ads to Clinton's 495.)

That's in part because — unlike Michigan — it comes in a lull in the calendar when few states are voting. Sanders has done best in states that he has been able to "spend time and concentrate on," says Matt Grossmann, director of the Institute for Public Policy and Social Research at Michigan State University.

Andrew Burton/Getty Images

2) Another big factor that suggests Sanders could pull off a big upset is the state's "open primary" system, in which voters can register on Election Day.

"Clinton does best with bread-and-butter Democrats who like the party," says Barry Burden, director of the Elections Research Center at the University of Wisconsin Madison. "Sanders does better with independents, and I think the open primary will facilitate that through one-stop shopping."

3) Minority voters will be much less of a factor in Wisconsin than they were in Michigan, where Detroit's voters represent a big portion of the electorate, according to Burden.

Additionally, some new polls have begun to suggest Sanders has been able to shrink the gap among black voters in Wisconsin, said Kathy Cramer, a political scientist at the University of Wisconsin Madison.

4) Wisconsin has a strong tradition of progressive voting similar to, though not as strong as, Minnesota. "There’s a long history of progressive, liberal candidates making their last stands here," one Sanders supporter in Wisconsin told the Washington Post.

5) The state has implemented a slew of new voter ID laws that could make it more difficult for minority voters in cities like Milwaukee to support Clinton, according to Wagner. (Though Wagner speculated that these rules could also work against Sanders by making it more difficult for young voters to cast their first ballots.)

Why Wisconsin might not hand Sanders the landslide he needs

But there are also a bunch of problems with the idea that Wisconsin will prove, like Michigan, much more friendly to Sanders than the polls predicted.

For one, despite the Michigan aberration, the polling in general this campaign has been pretty good at predicting primary results, according to the political scientists.

"I think we don't yet understand why the Michigan polls were so far off; they've been good elsewhere in the Midwest," Burden says.

Burden adds that, unlike the polls in Michigan, the research being done out of Wisconsin has largely been conducted by firms with strong methodologies and connections to the state.

"I think they're going to be pretty close to the result," Burden said, pointing to a Marquette University poll that had Sanders up by about 5 points over Clinton.

There's also a reason Michigan was so hard to predict: Since Obama wasn't on the primary ballot in 2008, it had been years since the state had a competitive Democratic primary, making it difficult to predict the demographics of the electorate. There should be no such difficulty in Wisconsin, Grossmann said.

And remember, we're still just talking about one state. There's not even consensus that a big win in Wisconsin would give Sanders a meaningful boost in the primary, Grossmann noted.

"The only thing left to really change the dynamic of the race is for Clinton to lose New York," he said. "That would be the big, flashing-light symbol that she has a big problem. Winning Wisconsin is not enough to show that Sanders has a big enough base of support."

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