MASSACHUSETTS — Six candidates are running in the Democratic primary for Massachusetts' 6th Congressional District, scheduled for September 1, 2026. The candidates are Beth Andres-Beck, John Beccia, Dan Koh, Mariah Lancaster, Tram Nguyen, and Jamie Zahlaway Belsito.

The incumbent, Seth Moulton, is not seeking re-election to the U.S. House of Representatives for this district, having decided to run for the U.S. Senate to represent Massachusetts. As of July 3, 2026, The Cook Political Report with Amy Walter, Inside Elections with Nathan L. Gonzales, and Larry J. Sabato's Crystal Ball rated the district as Solid/Safe Democratic.

Beth Andres-Beck, a senior staff software engineer, stated, "America could have good things: functional healthcare, honest government, safe schools, and a future we can take pride in building." She added, "I'm running for Congress because I believe we can have those things, not because we behave or wait our turn, but because we organize, show up, and believe in one another."

John Beccia, co-founder and chair of the financial services strategic consulting firm FS Vector, indicated his motivation for running on his campaign website. "John is tired of politicians making unkept promises and offering the same old solutions that don't work anymore," his campaign website states. It also says he is running "to do what he did in business: create jobs, protect consumers, and make our economy work for working people."

Dan Koh has experience in Washington, D.C., having served as a former chief of staff at the U.S. Department of Labor and a senior aide in former President Joe Biden's administration. He also hosts The People's Cabinet podcast. His campaign website states, "Dan Koh is running for Congress because Donald Trump is trampling our constitution and American way of life, and we need leaders fighting back to defend our Democracy, protect our rights, reduce the cost of living, and stand up for families and communities like ours."

Mariah Lancaster, a veterinarian, also has experience in Washington, D.C., where she previously served as a foreign affairs officer at the State Department and as a science policy advisor and legislative staff in the U.S. House of Representatives. Her campaign website indicates she "will keep money in the pockets of hardworking Americans by fighting for universal healthcare, affordable housing, equitable and accessible education, and to keep safe, healthy food on every kitchen table across America."

Tram Nguyen is a state legislator and an attorney, representing the 18th Essex District in the Massachusetts House of Representatives. Nguyen stated, "I am the only candidate with current legislative experience." Her campaign website says, "Now Tram is running for Congress to tackle the high cost of living, expand affordable housing, protect fundamental freedoms, and restore trust in our democracy."

Jamie Zahlaway Belsito has experience in Washington, D.C., and founded the Maternal Mental Health Leadership Alliance. She said, "While Trump wages war on our democracy, too many Democrats argue about whether we need to abandon transgender Americans or abortion rights." Belsito added, "I'm a Democrat who won't apologize for human rights, universal healthcare, and a fair economy with good union jobs."

Why It Matters

This primary election is one of 58 races for the U.S. House of Representatives in 2026 where an incumbent is not seeking re-election. In 2026, 22 Democrats and 36 Republicans are not running for re-election. The outcome will determine the Democratic nominee for a district rated as reliably Democratic, following incumbent Seth Moulton's decision to pursue a U.S. Senate seat.