The 2026 US primary season has ended after seven months of upheaval, featuring major defeats for political incumbents, costly Senate battles and evidence that both President Trump’s influence and the Democratic Party’s internal divisions remain powerful forces.
The final contest took place in Delaware on Tuesday, bringing an end to a cycle marked by candidate withdrawals, unexpected upsets and fierce struggles between establishment figures and insurgent challengers.
Trump’s influence reshapes Republican contests
Republicans lost more incumbent Senate seats than Democrats, with two senators opposed by Mr Trump defeated in their primaries. John Cornyn lost in Texas to Ken Paxton, the scandal-plagued state attorney general, while Bill Cassidy of Louisiana failed to reach a runoff after Mr Trump backed a challenger.
The Texas contest was the most expensive Senate primary of the season, costing more than $130 million. Mr Paxton won despite being outspent by roughly eight to one on advertising and will now face James Talarico, a contest that has left Republicans nervous about retaining the seat.
May was Mr Trump’s strongest month of political retribution. Within four days, his endorsed candidates defeated Mr Cassidy and Thomas Massie, a seven-term Kentucky congressman and prominent critic of the president and the Iran war. Mr Trump’s backing also helped Mr Paxton overcome Mr Cornyn, whom the president viewed as insufficiently loyal.
His influence was not universal, however, with some candidates he supported going on to lose later in the primary season.
Democratic incumbents face a left-wing challenge
Seven Democratic members of the House were defeated in their primaries, compared with four Republicans. Four of the Democratic challengers described themselves as democratic socialists, reflecting a desire in several districts for younger and more progressive representatives.
June was particularly successful for the Democratic Socialists of America. Darializa Avila Chevalier in Manhattan and Claire Valdez in Queens won House primaries, while former DSA member Brad Lander defeated Dan Goldman in New York. In Colorado, 29-year-old Melat Kiros unseated 15-term representative Diana DeGette.
The Democratic establishment suffered one of its clearest setbacks in Michigan, where Haley Stevens lost a Senate primary to Abdul El-Sayed. Ms Stevens had the backing of Chuck Schumer and Michigan governor Gretchen Whitmer, as well as more than $60 million in outside advertising, but was defeated by Dr El-Sayed, a progressive critic of Israel who was outspent by nine to one.
In Florida, Angie Nixon produced another major upset by defeating Alex Vindman in the Democratic Senate primary. Ms Nixon, a democratic socialist in the state legislature, ran on a shoestring budget against the moderate former national security official and described the result as a victory “for the little guys and girls.”
The left did not win everywhere. Francesca Hong, who had become the overwhelming favourite in the Wisconsin governor’s primary, was beaten by moderate candidate David Crowley. The result was one of several significant polling failures during the season.
Unusual routes to the ballot
Maine Democrat Troy Jackson took just 17 days to announce his Senate campaign and win his party’s nomination at an unusual convention. He was chosen to replace Graham Platner, an oysterman who withdrew after an accusation of rape, which he denied.
Mr Jackson, who lost a bid for governor earlier in the year, now faces a short campaign against Senator Susan Collins, regarded as one of the most vulnerable incumbents.
South Carolina offered an even more abrupt political ascent. Darline Graham entered the Senate after the death of her older brother, Lindsey Graham, being sworn in three days later to complete the final months of his term. With Mr Trump’s support, she then narrowly won a runoff for the full term only 45 days after his death.
Her campaign also produced one of the season’s most striking moments of candour. Asked about Taiwan during a debate, she said: “I’m just going to be honest here. I’m not that informed on national security.” She nevertheless won the nomination.
In Alaska, a middle initial became a central feature of the Senate contest. Republican Senator Dan S Sullivan is running for re-election against another Dan Sullivan, Dan J Sullivan. Republicans have accused the second candidate of being placed on the ballot by Democrats to confuse voters, an allegation he denies. He does not campaign extensively, while Democrats hope former representative Mary Peltola can capture the seat.
Republicans also emerged from the redistricting battle in a stronger position. After Mr Trump urged Texas Republicans to redraw House maps midway through the decade, Democrats attempted to respond with their own changes. Republican-backed maps, helped by rulings in state and federal courts, could produce an estimated five to 10 additional House seats.
The season ended with one final reminder that political campaigns do not always follow conventional rules. Tom Smith won a Michigan congressional primary despite having suspended his campaign, filed no campaign report, run no adverts and endorsed another candidate. Voters in the Flint region selected him over Amir Hassan, the Trump-backed candidate.
Scott Brown, meanwhile, took a more relaxed view of defeat after losing the New Hampshire Republican Senate primary to John E Sununu by more than 40 points. Before the vote, Mr Brown said his plan if he lost was to “Work out, drink and go gamble and come home and take a nap for a day or two.”
“Life,” he said, “goes on.” The primary season is over, and the candidates now turn to the general election.
