Stefany Shaheen holds the lead in the September 8 Democratic primary for New Hampshire’s open 1st Congressional District seat, driven by her consistent advantage in University of New Hampshire and Saint Anselm College polling plus endorsements from every Democratic mayor in the district. Traders assign her the highest implied probability at 57.5 percent, reflecting her strong name recognition as the daughter of U.S. Senator Jeanne Shaheen. Maura Sullivan follows at 31 percent amid solid first-quarter fundraising and her background as a Marine veteran and former Obama administration official, though she trails in surveys. Recent candidate forums in Manchester have centered debate on housing affordability, healthcare access, and immigration enforcement, while high undecided shares in available polls leave room for shifts before the open-seat contest.