Working the phones, banging on doors, even pressing her fiancé, 22-year-old Claudia Zavala is determined to get as many Bernie Sanders voters as she can around St. Cloud in Minnesota’s Tuesday primary.

Adeline Wright, a Sanders “early adopter,” plies customers at her Duluth hair salon with Sanders campaign material to “shine my little light a little brighter” for the left’s populist candidate.

Kevin Chavis, in Minneapolis, has spent the past year rounding up volunteers. “The momentum and movement is toward Sanders,” the 38-year-old Sanders devotee said confidently.

In a show of force, Sanders will rally his die-hard supporters Monday at a concert at the 18,000-seat St. Paul RiverCentre. That will come on the eve of a primary that could be a key test of the momentum he has built up in the race for the Democratic nomination. Although he won the state’s Democratic caucuses four years ago, he faces popular home-state senator Amy Klobuchar and a growing chorus of Democrats alarmed at the prospect of nominating an aging democratic socialist with uncertain prospects of beating President Donald Trump in November.

The 78-year-old senator from Vermont isn’t the only candidate courting voters here ahead of the Super Tuesday primary. Campaigns are deploying surrogates and volunteers, holding events and running TV ads through the weekend. But Sanders appears to be making one of the biggest and most aggressive plays to win Minnesota, a state he carried with 60% support in the 2016 caucus.

While the Sanders movement appears to have hung on in Minnesota, the state’s new primary system is expected to bring out more mainstream voters than the sort of party activists who flocked to Sanders’ side in the caucuses. Many felt cheated when Hillary Clinton won the nomination. Now they smell redemption.

“I think that in 2016, I just remember feeling like this is so amazing … but how could this ever happen? There is so much work to do,” said Naomi Hornstein, who spent Friday afternoon texting voters from the TakeAction Minnesota office in St. Paul. “And now I’m seeing it’s really, really possible.”

Organizers with the Sanders campaign, which has 12 paid Minnesota staff members and field offices in Mankato, Minneapolis and St. Paul, have knocked on 52,000 doors and hosted 500 voter events in recent months. Independent groups supporting Sanders’ bid, including the 50,000-member TakeAction Minnesota and local chapters of Democratic Socialists of America, have staged outreach of their own.

The effort comes amid projections of a close race in Minnesota, where 75 pledged delegates of the roughly 1,900 needed to win the nomination are up for grabs. A Star Tribune/MPR Minnesota Poll, conducted ahead of the Nevada caucus, showed Sanders within striking distance of Klobuchar, who leads with 29% support. The political publication FiveThiryEight rates the race as a “tossup” between the two.

Klobuchar is also making a final push to shore up her home state, running ads and deploying top DFL lawmakers such as U.S. Sen. Tina Smith and Rep. Dean Phillips to campaign on her behalf. She will host a final rally of her own at St. Louis Park High School on Sunday night.

Klobuchar has staked much of her campaign on electability, and that remains the chief concern of moderate Democrats looking for an alternative to Sanders. In debates, Klobuchar has pounded Sanders on his inability to account for the public costs of his signature Medicare for All proposal, which she argues would knock millions off private employer health plans.

Critics have pointed to Sanders’ age, a recent heart attack and his reluctance to release his full medical records. He’s also faced backlash for praising literacy programs under the late Cuban dictator Fidel Castro. In the main, the establishment case against Sanders rests on what many see as an improbable White House bid — and the down ballot risk that goes with it.

Phillips, running for re-election in a suburban swing district, said he thinks a Sanders nomination could hurt Democrats in districts like his, helping hand the House back to the GOP in November. Gov. Tim Walz, who is also backing Klobuchar, has echoed those concerns.

Cindy Rugeley, head of the political science department at University of Minnesota Duluth, said those wary of Sanders’ ability to lead the top of the ticket could have a legitimate fear.

“A lot of independents are saying, ‘I don’t like Trump but I can’t go with Bernie.’ A lot of the Republicans who say, ‘Give me an alternative to Trump,’ are not going to vote for Bernie,” Rugeley said. “Not only does he have to get enough voters to overcome what Trump will get, he has to get enough voters to overcome what he will lose, just because he’s him.”

Sanders’ supporters vehemently disagree, arguing that a ballot without their candidate will be worse for turnout.

“I think anyone else at the top of the ticket is going to depress the vote because Bernie has such an energetic army of volunteers,” said Rita Allen, co-chair of Twin Cities Democratic Socialists of America. “I can’t see any other candidate’s supporters wielding that kind of energy.”

Sanders’ supporters say energy — and organization — is on their side. They point to efforts to build a diverse coalition that could turn out droves of new voters, including those who aren’t registered yet. Recent outreach efforts have targeted students, Spanish speakers, public housing residents and other demographic groups that voted in lower numbers in the past.

“Bernie has the rainbow coalition at his back,” said Attorney General Keith Ellison, one of the most prominent Minnesotans backing Sanders. “… We have a diverse, very, very representative voting base behind him in Minnesota and the country.”