Former U.S. Senator John E. Sununu officially entered the 2026 race in New Hampshire, campaigning to succeed retiring Democratic Senator Jeanne Shaheen. In his launch video, Sununu told voters: “Congress just seems loud, dysfunctional, even angry. I want to return to the Senate to help calm the waters.”

Sununu served three terms in the House before defeating then-Governor Shaheen in 2002 to win the New Hampshire Senate seat; he lost the rematch in 2008. His return comes nearly two decades after leaving public office for the private sector.

For Republicans, this is a golden opportunity. New Hampshire is the region’s only true swing state, and with Shaheen stepping aside, the seat opens up in a cycle where the GOP seeks not just to defend but expand its Senate majority. National Republicans believe Sununu brings strong name recognition and credibility in the Granite State.

Still, the path is not automatic. Sununu must first secure the GOP nomination. His strongest competition comes from former Senator and Ambassador Scott Brown. Brown has leaned into the Trump-era base, emphasizing his alignment with President Trump’s agenda and fundraising heavily. He’s already called out Sununu’s past independent streak, pointing to his backing of John Kasich in 2016 and Nikki Haley in 2024, as well as his published op-ed branding Trump a “loser.”

President Trump has remained officially neutral so far. While that leaves Sununu without an immediate endorsement booster, it also leaves room for maneuver. Reports suggest national Republican strategists view Sununu as the strongest candidate to flip the seat — a flip that would not only return it to the GOP column, but help lock in and expand the Senate majority Republicans are aiming for.

Sununu emphasized the campaign will focus on Granite State issues such as healthcare affordability, energy costs, housing and border security, rather than Washington partisan squabbling. He said: “Maybe you’re surprised that I’m running for the Senate again. I’m a bit surprised myself. Why would anyone subject themselves to everything going on right now? Well, somebody has to step up and lower the temperature. Somebody has to get things done.”

In short: the Republican field now features a heavy-hitter with deep state roots, strong ties to New Hampshire, and a credible path to winning in 2026. The GOP has the chance to turn this open seat into a win — but Sununu will have to navigate primary politics, reconcile his past positions with today’s Republican base, and secure key endorsements to prevail.

Sununu & Trump: A Complicated Relationship

Understanding Sununu’s past interaction with Trump helps clarify the dynamics at play in this race.

Background of Sununu’s past opposition

• In 2016, John E. Sununu served as a national co-chair for John Kasich’s presidential campaign. He did not support Trump’s 2016 bid.
• In the 2024 Republican primaries, Sununu backed Nikki Haley rather than Trump.
• He authored an op-ed published just ahead of the New Hampshire presidential primary with the blunt headline “Donald Trump is a loser.”

Why this history matters

• That record means Sununu begins the 2026 Senate contest with baggage in the Trump-aligned wing of the party. Some voters will view him skeptically if they believe loyalty to Trump is a key litmus test.
• On the other hand, his independence also offers advantages: he can appeal to moderate Republicans, independents and swing voters in New Hampshire who may have turned off by raw partisan rhetoric. Because New Hampshire is a swing state, that broader appeal could be a strategic asset.

Where Trump stands (so far)

• Trump has not yet endorsed in the New Hampshire GOP Senate primary, leaving the field open.
• While Trump once publicly signaled support for Sununu’s brother (former Governor Chris Sununu) in a possible Senate run, John E. Sununu must still make his case to the President and his base.
• Some Republican strategists believe that Trump may be pragmatic — if Sununu emerges as the strongest candidate to flip the seat, the president could be willing to support him despite the earlier friction. As one adviser put it: “President Trump appreciates winners … and understands that John E. Sununu puts this race on the map for Republicans.”

What Sununu must do

• He needs to demonstrate to GOP primary voters that, despite his past, he is committed to key Republican priorities (border security, low taxes, energy independence, etc.).
• He may need to secure Trump’s endorsement — or at least neutralize opposition from the pro-Trump base.
• He needs to keep the campaign message centered on winning the seat back for Republicans, rather than internal Republican feuds.

Why a Sununu Win Matters for Republicans

• Seat flip potential. With Sen. Shaheen retiring, this is a rare open seat — and Republicans have a strong opportunity to convert it. Flipping a Democratic seat in a swing state is a direct path to expanding the GOP Senate majority.
• Midterm dynamics favoring Republicans. Holding a 53-47 majority after the next election would give Republicans greater flexibility on legislation, confirmations, and oversight. A successful 2026 campaign in New Hampshire would contribute meaningfully to that goal.
• Messaging advantage. A win in a northern swing state helps buck the narrative that Republicans can only win in deep red states. Demonstrating competitiveness in a place like New Hampshire strengthens the GOP’s appeal to independent and moderate voters.
• National momentum. Winning this seat could provide momentum going into 2028 and reinforce the party’s strategy of targeting vulnerable Democratic seats. It also signals to donors and activists that the GOP has a winning blueprint beyond the usual battlegrounds.

Bottom Line

John E. Sununu’s entry into the 2026 Senate race is a major development for Republicans. He brings name recognition, prior Senate experience, and a base in a state that is both competitive and critical to national Senate math. The complications with his past stance toward Trump are real — but not necessarily insurmountable