Rep. Seth Moulton (D-Mass.) announced on Oct. 15, 2025, that he will run to represent Massachusetts in the U.S. Senate in 2026 rather than for another term in the U.S. House of Representatives.

Politico’s Kelly Garrity wrote that “Moulton will challenge Sen. Ed Markey for his Senate seat in 2026, setting up one of the biggest tests of Democratic voters’ appetite for generational change following the 2024 presidential election.”

As of Oct. 14, 2025, independent race forecasters The Cook Political Report and Inside Elections have rated the general election for the seat as Solid Democratic. Sabato’s Crystal Ball rated it Safe Democratic.

On his campaign, Moulton said, “Real people across Massachusetts are being hurt by Democratic leaders refusing to do everything they can to win. We’ve got to look in the mirror and be honest. It’s time for change.”

In 2014, Moulton first ran for the U.S. House in Massachusetts’ 6th Congressional District. In the Democratic primary, he defeated incumbent Sen. John Tierney (D-Mass.) 50.8% to 40.1%. In the general election, Moulton defeated Richard Tisei (R) 53.6% to 40.2%. Moulton won re-election in 2018 by 34 percentage points, in 2020 by 31 percentage points, and in 2022 by 28 percentage points. He ran unopposed in 2016 and 2024.

As of Oct. 14, 2025, independent race forecasters The Cook Political Report and Inside Elections have rated the general election for the district as Solid Democratic. Sabato’s Crystal Ball rated it Safe Democratic.

As of Oct. 15, 2025, Moulton is one of 39 members of the U.S. Congress—eight U.S. Senate members and 31 U.S. House members—who have announced they will not seek re-election to their current seats in 2026.

Of the 31 representatives not seeking re-election:

• Eight—five Democrats and three Republicans—are retiring from public office.
• Twelve—six Democrats and six Republicans—are running for the U.S. Senate.
• Ten—all Republicans—are running for governor.
• One Republican is running for state attorney general.

Compared to the last four election cycles, there were 19 retirement announcements at this point in 2024, 22 in 2022, 25 in 2020, and 24 in 2018.

Between January 2011 to October 2025, Ballotpedia followed 333 announcements from U.S. House members who announced they would not seek re-election. January had the highest number of members announcing they would not run for re-election at 57. The fewest announcements took place in June at 15.