Abdul El-Sayed, an insurgent former public health official who harnessed Democratic frustration with the party establishment, narrowly defeated Rep. Haley Stevens in Michigan’s U.S. Senate primary, setting up a crucial test for progressives in a key battleground state.

El-Sayed will face Republican Mike Rogers, a former congressman, in November in a race that will help determine control of the Senate. His first challenge will be unifying Democratic factions after a bitter primary that offered divergent visions for a party desperate for a path back to power.

Stevens, who pledged her support for El-Sayed after conceding defeat, was backed by the Democratic establishment, including outgoing Sen. Gary Peters, whose retirement spurred a scramble to fill his seat. El-Sayed promised a more aggressive approach for confronting entrenched corporate interests and President Donald Trump, and declared his victory was nothing short of a political earthquake despite only scraping by Stevens.