Sen. Gary Peters of Michigan, who spearheaded the Democratic campaign in the Senate for the previous two election cycles, has declared that he will not run for a third term in 2026, opening up a fiercely contested battleground seat that both major political parties are likely to pursue.The 66-year-old’s shocking decision on Tuesday to resign after only two terms is unexpected and presents a challenge for Michigan Democrats at a time of upheaval, as they will probably have to split their strong bench between the 2026 Senate and gubernatorial contests.