New Hampshire’s September 8 primaries amount to something rare in American politics: a single election night that simultaneously measures the strength of a sitting president’s endorsement machine and the depth of an insurgent left’s momentum heading into the midterms. With Democratic Sen. Jeanne Shaheen retiring after three terms, the Granite State now hosts one of the most consequential open Senate seats in the country — and both parties are using Tuesday’s contests to answer uncomfortable questions about who actually controls their respective coalitions in 2026.
What Happened on the Ballot
On the Republican side, President Donald Trump has thrown his weight behind former Sen. John Sununu, who is seeking to reclaim the seat he lost to Shaheen in 2008 by roughly 6 percentage points. Sununu’s main rival is a familiar figure in New England politics: Scott Brown, the former Massachusetts senator who relocated north, ran for this same New Hampshire seat in 2014, and later served as Trump’s ambassador to New Zealand and Samoa during the president’s first term. The race is, in effect, a contest between two men with genuine Trump-world credentials — which makes the president’s choice of Sununu a revealing act of coalition management rather than an obvious loyalty play.
Democrats, meanwhile, are watching Rep. Chris Pappas attempt to hold off Karishma Manzur, a scientist and member of the Democratic Socialists of America who has centered her campaign on Medicare for All and sharp criticism of Pappas over his support and funding for Israel, which she has characterized as “enabling genocide.” Pappas, who has won a battleground House seat every cycle since 2018, is behaving like a general-election nominee already — running on cost-of-living economics and political corruption, and airing ads against a prospective Republican opponent. A divisive Democratic primary is also unfolding in Pappas’s open House seat, and a second incumbent House Democrat faces a challenge from the left, making the entire New Hampshire delegation a proxy battlefield for the party’s ideological future.
Why It Matters
The stakes begin with Senate math. Shaheen’s retirement transforms a reliably held Democratic seat into a genuine toss-up in a state with a long history of ticket-splitting — the same electorate that has sent Republicans to the governor’s mansion while backing Democrats for federal office. For Republicans, flipping this seat is not merely symbolic; in a chamber where margins have repeatedly been decided by one or two votes, New Hampshire could determine whether the GOP expands or squanders its governing majority in the final two years of Trump’s term. That is precisely why the president intervened in the primary at all: a wounded or underfunded nominee emerging from a Sununu-Brown slugfest would hand Pappas a head start in a race Republicans believe is winnable.
For Democrats, the Pappas-Manzur contest is the latest data point in a season in which the party’s left flank has punched above its weight in primaries nationwide. The strategic dilemma is acute and familiar: progressive challengers energize the base and dominate small-dollar fundraising, but general-election operatives worry that a democratic socialist nominee in a swing state would be a gift to Republican ad-makers. The Israel dimension adds a newer and more volatile variable. Since 2024, Democratic primaries have increasingly become referendums on the party’s Middle East posture, and Manzur’s willingness to use the word “genocide” against a sitting Democratic congressman reflects how thoroughly that debate has migrated from campus activism into formal electoral politics.
There is also an institutional story here about Trump’s endorsement record. Throughout his political career, the president’s backing has been most potent in open Republican primaries and weakest when he opposes candidates with independent standing in their states. Brown is not a token opponent — he has run statewide in New Hampshire before, retains name recognition, and can plausibly claim his own Trump service. If Sununu wins comfortably, it reinforces the narrative that the endorsement remains the single most valuable asset in GOP politics. If Brown prevails or keeps it close, it signals that even in 2026, with Trump in the White House, local political gravity has not been fully repealed.
Historical Context
New Hampshire has a long tradition of humbling national figures. The state’s 2016 Democratic primary delivered Bernie Sanders a 22-point victory over Hillary Clinton, an early warning of the party’s coming ideological reckoning. On the Republican side, the Sununu name itself is a piece of institutional history: John Sununu’s father served as governor and later as White House chief of staff under George H.W. Bush, and his brother Chris Sununu governed the state for four terms while maintaining a conspicuously arm’s-length relationship with Trump. A John Sununu victory powered by Trump’s endorsement would represent a remarkable reconciliation between the Bush-era Republican establishment and the party’s current populist leadership.
The late-calendar timing matters too. New Hampshire holds among the final primaries in the nation, which historically has meant nominees emerge with little time to heal intraparty wounds before November. In 2014, Scott Brown won his primary but could never consolidate a divided GOP electorate and lost to Shaheen. Republicans are keenly aware of that precedent as they watch Tuesday’s results.
What to Watch
Three indicators will tell the real story beyond the raw vote counts. First, the margin in the GOP primary: anything under a double-digit Sununu win suggests Trump’s endorsement is persuasive but not dispositive in states with established political brands. Second, turnout composition on the Democratic side — if Manzur overperforms among voters under 40 and in college towns like Hanover and Durham, expect a wave of national coverage framing the left as the party’s ascending force, regardless of whether she wins. Third, watch the money: within 48 hours, national Republican groups will signal through ad reservations whether they genuinely believe this seat is competitive, or whether Tuesday’s winner inherits an underfunded long-shot campaign.
Key Takeaway
Tuesday’s New Hampshire primaries are less about who wins than about what the margins reveal: whether President Trump’s endorsement still functions as a coronation in Republican politics, and whether the Democratic left’s 2026 momentum can survive contact with a swing-state general election. In a Senate race that could decide control of the chamber, both parties are about to learn how much ideological purity they can actually afford.
