Mr. Pappas, a 44-year-old Democratic congressman, is the first major candidate to enter the race to succeed the retiring Senator Jeanne Shaheen.

Former New Hampshire Gov. Chris Sununu’s (R) decision not to run for Senate is presenting a challenge for Republicans as they turn their sights on the state ahead of 2026. Sununu’s announcement was not necessarily surprising to Republicans.

Rep. Chris Pappas is entering the race for New Hampshire’s open Senate seat. The fourth-term congressman is the first high-profile candidate to launch a campaign to succeed Sen. Jeanne Shaheen, a fellow Democrat who is retiring after three terms.