Former Senator John Sununu secured victory in the New Hampshire Republican primary for the open U.S. Senate seat Tuesday, earning the endorsement of President Trump and setting up a November general election clash against Democratic Representative Chris Pappas.

Sununu defeated Scott Brown, the former Massachusetts senator who succeeded Ted Kennedy’s late seat in 2010, in what has been described as a decisive primary contest. The race followed Senator Jeanne Shaheen’s announcement of retirement from the Senate—a move that created the vacancy Sununu now holds. Both candidates previously lost to Shaheen: Sununu was defeated by her in 2008 and Brown by her in 2014 after relocating to New Hampshire.

Sununu, who served three terms in the U.S. House of Representatives and one term in the Senate, is the brother of former Governor Chris Sununu and son of former Governor John H. Sununu. Brown expressed confusion among voters about distinctions between his family members, noting that some conflated John E. Sununu with his brother or father.

The primary result positions Sununu directly against Pappas in November’s general election, a contest Democrats warn could determine control of the U.S. Senate. Polls indicate an extremely tight race, with Republicans already targeting Pappas over tax policy claims he made during his 2021 climate and social safety net advocacy.

“ heating up the race,” Sununu stated in his victory message, “As senator, I’ll have just one job: stand up for the people of New Hampshire every single day.” He added that he would “keep listening, keep working, and stay laser-focused on the economy, jobs, and making life more affordable.”

Sununu’s win follows a primary where he held 70% support against Brown’s 25% with about one-sixth of votes counted. Pappas, who first entered office in 2018, had positioned himself as the likely general election challenger but launched attacks on Sununu this August over tax breaks for pharmaceutical companies and insurance industry ties.