Incumbent Massachusetts Senator Ed Markey has won the Democratic primary, fending off a challenge from Representative Seth Moulton, the Associated Press projected on September 1, 2026. The victory positions Markey, an 80-year-old progressive, to seek a third term in the Senate.

The primary race was largely defined by a generational divide, with Moulton, 47, arguing for a new generation of leadership to tackle emerging issues like artificial intelligence. Markey, who has served in Washington since 1976, emphasized his extensive track record and experience.

Moulton, a Marine Corps veteran and member of the moderate New Democrat Coalition, sought to unseat the long-serving senator by highlighting differences in approach to modern challenges. He specifically pointed to the need for leaders who grew up with the internet and would face the long-term consequences of artificial intelligence.

Markey, endorsed by prominent progressive figures including Senators Bernie Sanders and Elizabeth Warren, and Representative Alexandria Ocasio-Cortez, countered by asserting his own leadership on technology safeguards. He cited his introduction of the Youth AI Privacy Act in March and stressed the importance of broad protections for emerging technologies.

This marks the second consecutive Senate primary in which Markey has defeated a younger Democratic challenger. In 2020, he successfully defended his seat against Representative Joe Kennedy III, who also represented a younger faction of the party.

Moulton gained national attention in 2018 for his efforts to block Nancy Pelosi's return as Speaker of the House, an action where he also advocated for new leadership.

Political science professor Raymond La Raja of the University of Massachusetts Amherst characterized Moulton's approach as "rolling the dice," noting his past presidential run and his decision to challenge an incumbent senator.

Despite agreeing on some policy points, such as abolishing U.S. Immigration and Customs Enforcement (ICE), the core of Moulton's campaign revolved around the generational argument. Markey, in turn, highlighted his ongoing engagement and proposed legislative solutions for issues like AI regulation, underscoring his continued relevance and energy in the political arena.