Left-wing Democrats have enjoyed a run of primary victories this summer, but face a critical test in Michigan, where progressive Senate hopeful Abdul El-Sayed is locked in a tight contest with moderate Congresswoman Haley Stevens ahead of the 4 August primary. The race highlights a deepening divide in the Democratic Party between its centrist establishment and an emboldened progressive wing, led by figures such as Bernie Sanders, Alexandria Ocasio-Cortez and New York Mayor Zohran Mamdani, as the party tries to work out how to win back Congress and the working-class voters who shifted to Donald Trump in 2024.

El-Sayed, a doctor campaigning on "Medicare for All" and opposition to US support for Israel's actions in Gaza, drew a large, enthusiastic crowd at a Detroit rally addressed by Sanders and Ocasio-Cortez. Stevens, by contrast, has secured backing from Michigan's governor Gretchen Whitmer and outgoing Senator Gary Peters, and has benefited from substantial corporate donations. The winner will face Trump ally Mike Rogers on 3 November for a seat Democrats must retain to have any chance of regaining Senate control, while a similar progressive test looms a week later in Wisconsin's governor's race.