Democratic Sen. Gary Peters won’t run for re-election in Michigan in 2026, creating a pivotal open Senate seat in one of the most tightly divided battleground states in the U.S.

The surprise decision Tuesday again complicates for Democrats in Michigan, who will be forced to defend an open seat in the battleground state for the second straight election cycle. Peters led the Democrats' Senate campaign efforts from 2021 to 2025 and helped the party hold control of the chamber in 2022 before Republicans flipped it last year.