When Jeanne Shaheen announced on March 12, 2025, that she would not seek a fourth term in the United States Senate, she ended a political career that had defined New Hampshire’s federal identity for nearly two decades — and set off the most consequential scramble for a Granite State Senate seat since she first won it in 2008.

Thirteen months later, the field has settled into a shape that tells you almost everything about the state of New Hampshire politics in 2026: a moderate Democratic congressman trying to move up, a Republican dynasty scion trying to come back, and a former Massachusetts senator trying to prove he belongs here. Hovering above all of it is a president whose approval rating in the state sits at 41 percent, a midterm environment that historically punishes the party in power, and a fight for the U.S. Senate majority that could come down to this single race.

New Hampshire hasn’t elected a Republican senator since Kelly Ayotte won her lone term in 2010. All four of the state’s congressional seats have been held by Democrats since 2017. But Republicans control the governor’s office, both chambers of the state legislature, and a majority on the Executive Council. The state is a paradox of partisan geography — blue at the federal level, red at the state level — and this race will test which gravity is stronger.

The Democratic Side: Pappas and the Moderate Lane

Chris Pappas was the first major candidate to enter the race after Shaheen’s announcement, declaring on April 3, 2025, after a 10-county listening tour that functioned as a soft launch. On paper, he is the most logical successor to Shaheen: a four-term congressman who already represents half the state’s population in the 1st Congressional District, a moderate who has broken with his party on high-profile votes like the Laken Riley Act, and a member of a family whose name recognition in Manchester rivals any political dynasty in the state. The Puritan Backroom, his family’s restaurant, is a required stop on the New Hampshire presidential primary circuit.

Pappas has consolidated institutional support with the speed of a candidate running unopposed. Shaheen endorsed him. So did Rep. Maggie Goodlander, who passed on a Senate bid of her own in April 2025 to seek re-election in the 2nd District. Former Rep. Annie Kuster endorsed him. Sen. Maggie Hassan endorsed him. The entire New Hampshire Democratic congressional delegation is behind him — a unified front that is rare in an open-seat race.

He faces two primary challengers: Karishma Manzur, a scientist and member of the New Hampshire Democratic Party Rules Committee who is running to Pappas’s left, and state Rep. Jared Sullivan, a first-term legislator from the North Country. Neither has approached Pappas’s fundraising or name recognition. His most recent FEC filing shows $2.27 million raised in the fourth quarter of 2025, with 96 percent of donations at $100 or less and no corporate PAC money. He entered 2026 with $3.2 million in cash on hand.

Pappas’s general-election strategy is already visible: run as the candidate who is actually from here, who has been doing the work, and who isn’t beholden to Washington or corporate interests. His campaign has hammered Sununu relentlessly on the lobbyist question, framing the race as a choice between someone who stayed and someone who cashed in.

But Pappas is not without vulnerabilities. His voting record in Congress — including support for some Biden administration priorities — will be tested in a state where the president’s approval sits at 41 percent and where voters punished Democrats at the state level in 2024 even while supporting Kamala Harris for president. Running for Senate also means vacating a House seat that Democrats can’t afford to lose, opening a competitive race in the 1st Congressional District that will divide party resources. And the question of turnout looms: Pappas’s coalition skews young, and midterm electorates skew old.

The Republican Primary: A Family Name and a Grudge Match

The Republican side of this race is, by any measure, stranger.

Scott Brown was the first Republican in, announcing his candidacy in June 2025 — months before Sununu made his move. Brown served as a U.S. Senator from Massachusetts from 2010 to 2013, lost to Elizabeth Warren, then moved to New Hampshire and lost to Shaheen in 2014 by 3 points. He later served as Trump’s ambassador to New Zealand and Samoa. His pitch is straightforward: he is the pro-Trump candidate, has been one since 2016, and has the grassroots credibility that Sununu — who called Trump “a loser” in the New Hampshire Union Leader on the eve of the 2024 presidential primary — does not.

Brown raised $1.2 million in his first full quarter but has been steadily outpaced since. His Q4 2025 haul was $374,000, and he entered the year with $907,000 in cash on hand. The Democrats have attacked him as a carpetbagger. Some Republicans have too.

John E. Sununu entered the race on October 22, 2025, and immediately reshaped it. The former senator — who served in the U.S. House from 1997 to 2003 and in the Senate from 2003 to 2009, before losing to Shaheen — is the son of former governor and White House Chief of Staff John H. Sununu and the older brother of former four-term Governor Chris Sununu. The name alone is worth double digits in a Republican primary.

Sununu’s entry drew endorsements from former Senator Judd Gregg, former Governor Craig Benson, state Senate President Sharon Carson, three members of the Executive Council, NRSC Chairman Tim Scott, and Senate Majority Leader John Thune, who reportedly recruited him. On February 1, 2026, President Trump endorsed Sununu on Truth Social, calling him an “America First Patriot” — a remarkable turn for a man who had backed John Kasich in 2016, endorsed Nikki Haley in 2024, and published an op-ed titled “Donald Trump is a loser” one day before the New Hampshire presidential primary.

The Senate Leadership Fund, aligned with Thune, declared that Trump’s endorsement “has put an end to the primary.” Brown disagreed. He remains in the race, telling supporters on social media that “the people of New Hampshire are the ultimate authority” and that “Senate seats are earned, not handed down.”

Sununu raised $1.36 million in Q4 2025 and claimed $1.7 million in his first two and a half months. But Pappas outraised both Republicans combined by more than half a million dollars in the same quarter.

Where the Polls Stand

The most recent comprehensive poll, conducted by Emerson College from March 21–23, 2026, tells a story of a race that is close and getting closer.

The topline: Pappas leads Sununu by 1 point (within the 2.9-point margin of error), but leads Brown by 9. If Sununu wins the primary, this is a coin-flip race. If Brown somehow pulls the upset, Democrats are heavy favorites.

The demographic breakdown is revealing. Women favor Pappas by 9 points. Men favor Sununu by 6. Voters under 40 break for Pappas by a staggering 23-point margin. Voters in their 50s and 60s favor Sununu by 12. Independent voters — who make up roughly 40 percent of New Hampshire’s electorate — disapprove of Trump at 59 percent, which could be a headwind for any Republican on the ballot.

Cook Political Report rates the race “Lean Democrat.” Inside Elections rates it “Tilt Democrat.” Both suggest the seat is competitive but that the structural environment currently favors Pappas.

The Money Race

Pappas is winning the money race by a wide margin. His $3.2 million in cash on hand heading into 2026 more than doubles Sununu’s $1.1 million and triples Brown’s $907,000. The no-corporate-PAC-money positioning is strategically important in a state where voters prize independence, and it sets up a clean contrast with Sununu, whom Democrats have branded as a lobbyist who “cashed in” at Akin Gump after leaving office.

But the money landscape will shift dramatically once the primary resolves. The Senate Leadership Fund and the NRSC have signaled heavy investment in New Hampshire if Sununu is the nominee. This race will ultimately be one of the most expensive in the country — outside spending could dwarf what the candidates themselves raise.

Sununu’s Trump Problem

The central tension of the Republican primary is the gap between what the party’s D.C. leadership wants and what its grassroots base in New Hampshire may demand.

Sununu’s anti-Trump record is extensive and well-documented. He co-chaired John Kasich’s 2016 presidential campaign. He endorsed Nikki Haley in 2024. He called Trump a loser in the state’s largest newspaper. Some MAGA activists in New Hampshire have called Trump’s endorsement of Sununu “a slap in the face to grassroots supporters.”

Brown has exploited this relentlessly. He has framed the race as a choice between a lifelong Trump supporter and a “Never Trumper” who is now trying to ride the party’s coat. When asked about his path to victory, Brown points to his ambassadorship under Trump, his early campaign presence in the state, and his work with grassroots activists. His line — “I stopped one political dynasty before, and intend to do the same in 2026” — is a reference to his 2010 upset win for Ted Kennedy’s long-held Massachusetts Senate seat.

But the math is not on Brown’s side. He trails Sununu by 29 points in the primary polling, is being outraised, and lacks the institutional support that Sununu has locked up. The more relevant question may be how much damage the primary inflicts on the eventual nominee. New Hampshire’s primary is one of the last in the nation — September 8, 2026 — giving the winner less than two months before the general election. If Brown goes scorched earth on Sununu’s Trump record through the summer, Pappas benefits from the wreckage without spending a dollar.

UNH political science professor Dante Scala has observed that Sununu’s message of lowering the temperature “sounds to me like a general election message, not so much a message that does much for the party base.” The question is whether Trump’s endorsement is enough to override the suspicion of voters who remember the op-ed.

The National Stakes

Republicans currently hold a 53–47 advantage in the Senate. They are defending seats in Ohio, Maine, and North Carolina against strong Democratic challengers. They are on offense in Michigan, Georgia, and New Hampshire. Democrats need a net gain of four seats to flip the chamber — a tall order, but not an impossible one in a midterm cycle with Trump’s approval underwater in multiple swing states.

New Hampshire is one of a handful of races that could determine control. If Democrats lose this seat without offsetting it elsewhere, the Senate is out of reach until at least 2028. If they hold it, the path to a majority narrows but remains alive — especially if the national environment continues to trend against the president’s party.

For Republicans, flipping Shaheen’s seat would be their most significant federal pickup in New Hampshire in 16 years and would provide a cushion against potential losses elsewhere. That is why Thune personally recruited Sununu, why the Senate Leadership Fund endorsed him within hours of his announcement, and why Trump swallowed his pride and endorsed a man who called him a loser in print.

What to Watch

Five months remain before the primary. Eighteen months of general-election positioning have already occurred. The shape of the race is clear, but several dynamics could reshape it.

First, whether Brown drops out. If he does, Sununu consolidates the Republican base and pivots to the general election with months of runway. If he doesn’t, the primary becomes a test of whether Trump’s endorsement can override his own grassroots voters’ instincts.

Second, the national environment. Trump’s approval in New Hampshire stands at 41 percent. If the Medicaid cuts from the One Big Beautiful Bill Act begin to bite — with up to 29,000 Granite Staters at risk of losing coverage — health care could become the defining issue of the fall campaign. Pappas, who has positioned himself as a fighter against corporate special interests and a defender of working families, is well-positioned to run on that ground. Sununu, who spent his post-Senate career on corporate boards and at the lobbying firm Akin Gump, will face attacks from both sides on the question of whose interests he serves — and whether a return to Washington after 17 years makes him a fresh voice or a relic.

Third, the Pappas coalition. His strength with young voters (a 23-point margin among those under 40) is remarkable but depends on turnout in a midterm year. His weakness with voters in their 50s and 60s (down 12 to Sununu) suggests he needs to expand his appeal among older moderates — a demographic that could be persuadable on health care, Social Security, and the cost of living.

And fourth, money. Once outside spending floods the state, the character of the race will change. New Hampshire is a small media market. It doesn’t take much to saturate the airwaves. Expect both sides to spend aggressively, and expect the attacks on Sununu’s lobbying career and on Pappas’s voting record to become unavoidable by summer.

This is the most consequential Senate race New Hampshire has seen since Shaheen first beat Sununu in 2008. The irony is that the race to replace her may come down to the same family name she ran against then — just with 18 more years of political baggage, a transformed Republican Party, and a state that keeps telling both parties the same thing: we’ll vote for you, but don’t assume you’ve earned it.

The filing period opens in June. The primary is September 8. The general election is November 3. New Hampshire will make its choice. As always, it will make both sides work for it.