Shaheen's retirement opens NH's first Senate vacancy since 2010, but Pappas starts in a strong position — he represents half the state in NH-01, outraised both Republican candidates combined in Q4 2025, and leads all GOP contenders in head-to-head polling. Sununu (82% on Polymarket) has Trump's endorsement and NRSC backing for the primary, but Brown is staying in, forcing a bruising contest through the late September 8 primary while Pappas runs unopposed. Sununu hasn't won an election in nearly two decades, and Trump's endorsement may help him in the primary but complicates his general election pitch in a state that went for Harris. NH independents who want to vote for an idiosyncratic Republican will have Ayotte on the ballot for governor — that valve makes ticket-splitting toward the Senate Democrat easier, not harder. Likely D.