Progressive Abdul El-Sayed was on the precipice of a Democratic primary win in Michigan on Wednesday morning, clinging to a narrow lead in an extremely tight race against Rep. Haley Stevens for the Democratic Senate seat.

A win for the progressive would come as a shock to the Democratic establishment and for AIPAC, D.C.’s top Israel lobby, which spent tens of millions of dollars supporting Stevens’ campaign.

He ran as the clear progressive choice in a three-way race that narrowed in July with the exit of state senator Mallory McMorrow, who was once seen as a middle candidate that could reach both progressives and centrists. McMorrow gained initial steam but ultimately collapsed after criticizing El-Sayed for appearing on a Twitch stream with Hasan Piker, a popular progressive streamer whose comments about Israel have been criticized as antisemetic by some.

El-Sayed locked up support from the party’s progressive wing in Congress, including from Senators Bernie Sanders, Elizabeth Warren, and Rep. Alexandria Ocasio-Cortez. As a result, his win would be a major rallying cry for the movement, which scored several commanding victories in House primaries against Democratic incumbents this cycle.

The battle between El-Sayed and Stevens turned intensely bitter over the last month. Supporters of both candidates attacked each other for language and social media attacks that Stevens supporters like Rep. Hillary Scholten (D-Mich.) called sexist, and language regarding both Piker and El-Sayed himself that many viewed as Islamophobic.

Concerns about electability also hovered closely over the race. El-Sayed’s ties to the progressive wing and support for progressive stances remain viewed by establishment-lane Democrats as a potential hindrance, should he face Republican former Rep. Mike Rogers for the seat in the fall.

Sen. Gary Peters, the moderate incumbent who chose not to run for re-election this year and put the seat into play, endorsed Stevens in the waning weeks of the race, as did Michigan Gov. Gretchen Whitmer.

Part of the reason for his victory was that progressives were able to fire those arguments right back at their centrist opponents. Stevens’ support from AIPAC, which was at times providing the majority of her campaign’s overall financial support and the sheer scale of the out-of-state and corporate PAC money backing her bid led many to question how strong of a candidate she could be if she was still losing to El-Sayed despite massively outspending him. Some of those same progressives questioned why AIPAC, which famously supports both Republicans and Democrats, including MAGA-aligned conservatives, would continue spending on her behalf against Rogers, who is also pro-Israel like Stevens.

El-Sayed and Rogers will face off for a seat that is central to Democrats’ pathway to winning back the Senate this year. The party needs to pick up four seats to win a majority, and holding the Michigan seat is key to that calculus. Aside from holding the line in the Great Lakes State, the party is eyeing pickup opportunities in Texas, Alaska, Ohio, North Carolina and Maine.