Incumbent U.S. Senator Ed Markey (D-MA) defeated a primary challenge from Representative Seth Moulton (D-MA) on Tuesday, September 1, 2026. Decision Desk HQ projected Markey as the winner shortly after polls closed. With 10% of the results reported by 9:05 p.m., Markey held 69.5% of the vote compared to 30.5% for Moulton.
The contest centered on a debate over leadership longevity and generational change. Markey, 80, has served in the Senate since 2013 following 20 terms in the U.S. House of Representatives. Moulton, 47, is a six-term congressman and Marine Corps veteran who argued during the campaign that the Democratic Party required a new generation of leaders and suggested that Congress should adopt upper age limits.
Markey received endorsements from Senator Elizabeth Warren (D-MA), Senator Bernie Sanders (I-VT), and Representative Alexandria Ocasio-Cortez (D-NY). Moulton was endorsed by The Boston Globe, which cited a need for "new vision" in the party. During their debates, the candidates clashed over LGBTQ rights, with Markey characterizing himself as an energized opponent of the Trump administration's agenda.
The scale of the victory, a margin of 39 percentage points based on early returns, follows a 2020 contest where Markey defeated another challenger, then-Representative Joe Kennedy III, by roughly 10 percentage points. The primary contest follows an internal party debate regarding age and term limits, particularly after President Biden’s exit from the 2024 presidential race and the deaths of several members of Congress.
What happens next: Markey will advance to the general election on November 3, 2026. He will face Republican John Deaton, an attorney who ran unopposed in the GOP primary. If successful in November, Markey will serve alongside Senator Elizabeth Warren. Moulton currently represents Massachusetts' 6th Congressional District.