Sen. Martin Heinrich of New Mexico endorsed Graham Platner on Tuesday in Maine’s Democratic Senate primary — the latest sign of a growing push inside the party against Senate Minority Leader Charles E. Schumer’s preferred candidate, Gov. Janet Mills.
“Graham Platner is focused on delivering for Mainers, not billionaire donors,” Mr. Heinrich said in a statement. “And he’s exactly the person the Democratic Party needs to win back working people.”
The 54-year-old added, “Every day, Graham’s building a movement around the folks who work hard for their family and their community — folks who deserve a Senator that fights in their corner.”
Mr. Platner, 41, is a combat veteran and oyster farmer running for public office for the first time. He argues that an agenda rooted in economic populism is the only way for the party to rebuild trust with working people who feel the system is stacked against them and tilted toward big corporations and the ultra‑wealthy.
In Ms. Mills, 78, he’s facing a two-term governor who entered the race in October after being encouraged by Mr. Schumer. The Democratic Senatorial Campaign Committee has also thrown its support behind her.
Mr. Heinrich’s endorsement follows one from Arizona Sen. Ruben Gallego, who called Mr. Platner “the kind of fighter Maine hasn’t seen in a long time.”
Vermont Sen. Bernard Sanders, 84, has also backed him.
Together, the endorsements mark a small but notable group of senators willing to break with party leadership in one of the most closely watched Democratic primaries of the 2026 cycle.
NBC News reported last month that Shawn Fain, president of the United Auto Workers, which has endorsed Mr. Platner, and other labor unions have urged Mr. Schumer and the DSCC to stay out of the race.
Maine is the only Republican-held Senate seat up this year in a state carried by Democratic presidential nominee Kamala Harris in 2024, making it a critical target for Democrats hoping to retake the Senate majority. The party needs a net gain of four seats to do so.
Mr. Schumer, 75, has described Ms. Mills as “the best candidate to retire Susan Collins.”
He highlights how the governor is the only Democrat to win statewide in Maine in the past two decades.
Even so, Mr. Platner has posted double‑digit leads in some recent polls. His campaign also survived a rough patch last year, when old offensive Reddit posts resurfaced and critics pointed to a chest tattoo he later covered because it resembled a Nazi symbol. He said the posts came during a period when he struggled with post‑traumatic stress disorder after his military service and that he has since changed.
The primary is June 9, and the winner will face Sen. Collins, 73, who is seeking a sixth term.
