BOSTON (AP) — U.S. Rep. Seth Moulton cruised to victory in Tuesday’s Democratic primary, defeating two challengers vying for his seat in Massachusetts’ 6th congressional district.

A former combat veteran in Iraq, where he served with the Marine Corps, Moulton’s win means almost certain re-election in the November general election to represent the predominantly Democratic district for a fourth term.

The 41-year-old launched an unsuccessful bid for president, exiting the crowded race last August. Moulton had focused his White House candidacy on mental health treatment after revealing his own struggles on that front as a war veteran. He was first elected to the U.S. House in 2014.

Moulton, of Salem, defeated Democrats Jamie Belsito and Angus McQuilken, both of Topsfield, and will face Republican John P. Moran on Nov. 3. The district covers parts of Middlesex and Essex counties, west and north of Boston.

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THIS IS A BREAKING NEWS UPDATE. AP’s earlier story follows below:

Candidates in four of Massachusetts' nine congressional districts are competing in Tuesday's primary for the chance to represent their party in the November general election.

In Massachusetts, a state with an all-Democratic congressional delegation, the winner of the primary is often seen as the presumed front-runner in the general election, meaning a lot is hanging on the primary vote tallies.

In the 1st Congressional District, incumbent U.S. Rep. Richard Neal — chairman of the powerful House Ways and Means Committee — is trying to fend off a challenge from Holyoke Mayor Alex Morse.

Morse, 31, has positioned himself as a progressive alternative to the 71-year-old Neal, who was first elected to represent the sprawling western Massachusetts district in 1988. Morse has the backing of New York Democratic Rep. Alexandria Ocasio-Cortez, while Neal has the endorsement of House Speaker Nancy Pelosi.

In the 4th Congressional District, seven Democratic candidates are seeking the seat being vacated by Democratic Rep. Joe Kennedy III, who opted not to seek reelection and instead challenge Sen. Edward Markey in the U.S. Senate primary.

The candidates include Jake Auchincloss and Becky Grossman — both members of the Newton City Council — former Brookline select board member Jesse Mermell, City Year co-founder Alan Khazei, epidemiologist Natalia Linos, former Wall Street regulator Isshane Lecky, and Ben Sigel, who worked for the Democratic National Campaign Committee.

Two Republicans are also running for Kennedy’s seat — Julie Hall and David Rosa. Both are veterans.

The district winds from the Boston suburbs of Newton and Brookline south through Attleboro, Taunton and Fall River.

In the 6th Congressional District, Jamie Belsito and Angus McQuilken are hoping to defeat incumbent U.S. Rep. Seth Moulton, a Marine Corps veteran who saw combat in Iraq and mounted a brief campaign for president last year.

Belsito, a self-described progressive, founded the Maternal Mental Health Leadership Alliance, which advocates nationally for better maternal health policies. McQuilken co-founded the Massachusetts Coalition to Prevent Gun Violence after the 2012 massacre at Sandy Hook Elementary School in Connecticut.

The district includes Salem, Gloucester and Newburyport.

In the state’s 8th Congressional District, which stretches from portions of Boston south to Bridgewater, Robbie Goldstein, a 36-year-old South Boston resident, is challenging longtime incumbent Rep. Stephen Lynch.

Goldstein, an infectious disease specialist and doctor at Massachusetts General, said he’s had a front row seat to what he considers the federal government’s disastrous handling of the coronavirus pandemic. He also sees himself as part of a wave of younger Democratic candidates trying to push the party toward a more progressive agenda.

Lynch, a former iron worker and labor leader who was born and raised in South Boston, is hoping to retain the seat he’s held since 2001. Lynch has pitched himself to voters as a fighter for working families.

While Tuesday is primary day, nearly 1 million Massachusetts voters had already cast ballots at early voting locations, by mailing them in or by depositing them in drop boxes due to fears of spreading or becoming infected with the coronavirus.

Secretary of the Commonwealth William Galvin, a Democrat, said Monday he still expects a few hundred thousand voters will still show up at polling locations on Tuesday to vote in person.