The rise of Bernie Sanders’ preferred Senate candidate in Michigan is frustrating moderates, delighting progressives, and testing the sway of Democratic leaders in a race that will likely determine the party’s shot at a Senate majority.

Abdul El-Sayed is gaining momentum in a divisive three-way Democratic primary with an uncompromising argument for clarity on progressive priorities — Medicare for All, abolishing ICE, and ending US military aid to Israel. The nomination is up for grabs among him, Rep. Haley Stevens, and state Sen. Mallory McMorrow, but El-Sayed is catching on with the base and just had his best poll.

Scattered general-election polling shows El-Sayed with the toughest path to beat the GOP’s consensus nominee, former Rep. Mike Rogers, whose lack of a serious opponent is letting him build his case for November ahead of the Democrats. But the party has to stay invested in Michigan, no matter who is the nominee, to keep its hopes for a Senate majority alive.

Which has left some Democrats sweating the prospect that El-Sayed prevails in August, only to get hammered by Rogers as too far left for a swing state.

“Of course,” one Democratic senator said when asked whether the party worries about El-Sayed losing in November. “Elissa Slotkin won by 19,000 votes against the same opponent. He’s pretty well-established, there’s not a divisive primary on the Republican side, and there are some really tough issues.”

Strategists who support Stevens and McMorrow said that as the state party held its convention this month, the Democratic chatter shifted from an expectation that Stevens or McMorrow would prevail to fretting that El-Sayed could win. An Emerson poll showed El-Sayed jumping into a first-place tie with McMorrow; the spiking unpopularity of AIPAC has complicated its expected involvement on behalf of Stevens.

Senior Democrats still see Stevens as the best bet against Rogers and see her as viable in the primary via her base of support in the Detroit area. Sen. Catherine Cortez Masto, D-Nev., is backing Stevens because of her support with labor and Black voters, but also because she “will focus on talking to everyone in a state like that. Not just your base.”

“That’s my concern in a primary like that. In a swing state, it is the moderate over the progressive that wins,” Cortez Masto, a former campaign committee chair, told Semafor.

Minnesota Sen. Tina Smith, who met with both the “really skilled” El-Sayed and McMorrow, said she’s heard from colleagues concerned about El-Sayed’s electoral prospects. But she urged that other Democrats’ predictions “be taken with a grain of salt,” pointing to the neutrality of Michigan’s senators.

Sanders endorsed El-Sayed on the first day of his campaign and will rally with him on May 3. The Vermont independent told Semafor that voters “want men and women who have the guts to stand up and take on big money and interests.”

“He has a good chance to win the primary and an excellent chance to win the election,” Sanders added.

McMorrow, who built a large online following after a viral 2022 speech, got the harshest social media blowback of her career after comparing left-wing commentator Hasan Piker (an El-Sayed fan) to antisemitic white nationalist Nick Fuentes. She also has the most support among sitting senators and could bridge the divide between El-Sayed and Stevens.

Sen. Chris Murphy, D-Conn., said all three candidates are “strong” but that “she’s the strongest. I think she gives us the best chance to win.”

“I’m not here to criticize any of the Democrats. I’m for Mallory because she has built a strong grassroots campaign based on her demonstrated excellence as a fighter,” said Sen. Elizabeth Warren, D-Mass.