<p class="wp-block-paragraph">Dan Koh, a former aide to President Joe Biden, won the Democratic primary on September 1, 2026, to succeed Rep. Seth Moulton (D-MA) in Massachusetts’s 6th Congressional District.</p>
<p class="wp-block-paragraph">Koh received 41.1% of the vote when the Associated Press called the race, defeating five other candidates. Tram Nguyen finished second with 29.5%, while the remaining four candidates each received less than 15%.</p>
<p class="wp-block-paragraph">In his victory speech, Koh reflected on his family’s history, noting that his family immigrated to the United States from Lebanon, and his grandmother fled North Korea as a refugee.</p>
<p class="wp-block-paragraph">“I know that tonight, I stand on their shoulders,” Koh told supporters.</p>
<p class="wp-block-paragraph">Koh has a background in state and national politics, having previously served as a selectman in Andover, Massachusetts, and narrowly losing the Democratic primary for an open House seat to Rep. Lori Trahan (D-MA) in 2018 for the state’s 3rd Congressional District.</p>
<p class="wp-block-paragraph">He later served as chief of staff to former Boston Mayor Marty Walsh, and followed Walsh to Washington when Biden appointed him to lead the Labor Department. Koh was also deputy director of the White House Office of Intergovernmental Affairs during the Biden administration.</p>
<p class="wp-block-paragraph">Throughout his campaign, Koh emphasized his connections to the Biden administration, even as some Democrats have sought to distance themselves from Biden. He was the only House candidate in this election cycle to receive endorsements from both Biden and former Vice President Kamala Harris. Biden has endorsed only one other House candidate: Nikki Gronli, a former Agriculture Department official, who won the Democratic primary in South Dakota’s at-large congressional seat.</p>
<p class="wp-block-paragraph">Koh highlighted Biden’s endorsement in his campaign messaging. “This campaign is about building the kind of coalition that can actually deliver for working families,” Koh said in a campaign ad that ran last week. “President Biden, Vice President Harris, the AFL-CIO, and Democratic leaders across this district aren’t just endorsing a candidate; they’re backing a fight to take on Trump’s corruption and bring down costs for the people who sent us here to fight for them.”</p>
<p class="wp-block-paragraph">His campaign also released a phone call from Biden in May in which the former president urged voters to support Koh. “You will be one heck of a congressman,” Biden said. “Everything you and I fought for, everything we did to help ordinary people, is in jeopardy now in this administration, so we got to get you elected.”</p>
<p class="wp-block-paragraph">The 6th District seat became available after Moulton announced his challenge to 80-year-old Sen. Ed Markey (D-MA) in the Democratic primary, framing his campaign around the need for generational change. Moulton ultimately lost to Markey, who retained the Democratic nomination.</p>
<p class="wp-block-paragraph">The House contest occurs amid a competitive election cycle for incumbents.</p>
<p class="wp-block-paragraph">The Bay State has also seen a generational contest in another Democratic primary, where Rep. Stephen Lynch, 71, a former ironworker and senior member of the House Oversight Committee, fended off a younger progressive challenger in the state’s 8th Congressional District.</p>
<p class="wp-block-paragraph">Koh will face Republican Micah Jones, an Army veteran and lawyer who ran unopposed in the GOP primary, in the November election. The 6th District leans heavily Democratic, making Koh the favorite to win the seat in Massachusetts.</p>