In Massachusetts’ Sept. 1 Democratic primary elections, voters overwhelmingly sided with incumbents. Sen. Ed Markey handily defeated competitor Rep. Seth Moulton, and all eight incumbent members of the House of Representatives were victorious in their re-election bids.
Incumbents overcame an abundance of challengers across the state and a rising movement in the Democratic Party for younger, more progressive candidates. Ultimately, despite these undercurrents within the party, voters trusted the generally progressive track records of Massachusetts incumbents.
Congressional incumbents were challenged in primaries this year at 56.5%, the highest rate since 2014, according to a Ballotpedia report. Democratic challengers in particular have received increased attention, with seven Democratic representatives being unseated by primary opponents across the country.
According to Tufts Newhouse Professor of Civic Studies Brian Schaffner, the quantity of primary challenges tracks with the trend of parties not in the White House forging a new path.
“Usually the party out of power is the one that’s grappling more with divisions in the party about what the best path forward is for winning the next election,” he said.
In Massachusetts, Moulton forfeited his seat in the House to launch a high-profile challenge to Markey, a 50-year Congress veteran. Moulton, who has served in the House since 2015, centered his campaign around a need for generational change. He argued that the 80-year-old Markey had become too old to serve as a senator and legislate effectively on modern issues such as artificial intelligence.
“People ought to ask, what are you going to accomplish in the next six years that you haven’t been able to accomplish in the last 50?” Moulton asked in an August debate with Markey.
Moulton saw some early momentum, with a May Emerson College poll putting him just 5 points behind Markey. Schaffner cautioned that those results did not necessarily prove Moulton’s popularity, though.
“Polling primaries is really hard,” he explained. “Most people who are going to vote in the primaries haven’t thought a lot about who they’re going to vote for yet, and so, especially further out from the election, you might get noisy results.”
Several polls closer to the election favored Markey by over 25 points. Indeed, Markey trounced Moulton on election night, winning 64.7% of the vote to Moulton’s 35%.
Some have attributed Markey’s landslide victory to Moulton’s failure to make a convincing argument against Markey’s progressive bona fides from half a century in Congress and a decade in the Senate.
“The biggest thing that I saw in terms of anti-Markey stuff was just his age, and I think that people couldn’t really find anything else that was really bad about him,” Emma So, president of Tufts Democrats, said.
While Democrats faced challengers at a high rate this cycle, Markey ultimately did not fit the image of a vulnerable incumbent.
Most Democratic challenges in 2026 have been driven by higher pressure on Democratic lawmakers to win back power in Congress in the midst of a highly unpopular Trump administration.
“People feel helpless seeing the Trump administration doing things that they find so troubling and threatening to the values they hold that it reaches a point where it creates an opening for an insurgent movement within the party,” Professor of Political Science Deborah Schildkraut said.
In New York, progressive challengers Darializa Avila Chevalier and Brad Lander — who were supported by New York City Mayor Zohran Mamdani — defeated incumbent Reps. Adriano Espaillat and Dan Goldman, respectively, in a win for the progressive wing of the party and the Democratic Socialists of America.
Markey, though, was seen as the more progressive candidate in the race, including on issues such as healthcare, where he endorsed Medicare for All while Moulton stopped short, only endorsing a public option.
“I think that race was very much an outlier in terms of having a progressive incumbent being challenged by a moderate,” Boden Wise, vice president of Tufts Democrats, said.
In the races for Massachusetts’ nine House seats, challengers mostly ran to the left of incumbents but did not see much success.
Dissatisfaction with congressional leadership among progressives may not be felt as strongly in Massachusetts compared to other states, according to Schaffner. With officeholders in the state already being fairly progressive, convincing voters to vote for further left challengers was a hard sell.
“The Democrats who are already in office in Massachusetts are already pretty liberal,” Schaffner said.
Schildkraut highlighted the influence of the incumbency advantage, saying incumbents carry built-in benefits due to the length of their time in office.
“[Incumbents have] already won elective office, so they have a donor network. They may have funds from their previous election. They have built colleagues and relationships in office,” she said. “All that makes it really hard for challengers, whether it’s the primary or the general election.”
Massachusetts’ congressional nominees will move on to the general election on Nov. 3., where all are expected to face little Republican competition.
