Rep. Jake Auchincloss (D-Mass.) is openly breaking with his party by refusing to support Maine’s leading Democratic U.S. Senate candidate, Graham Platner, citing a chest tattoo critics say resembles a Nazi-era symbol.

In an interview with CNN on Monday, the lawmaker called Platner’s tattoo and his explanations for it “personally disqualifying.”

“I hope Maine voters agree with me,” Auchincloss said. “I think it would be a mistake for the Democratic Party to think that Graham Platner’s brand of the Democratic Party is what wins us durable majorities throughout this country.”

Platner, an Army veteran and oyster farmer, has faced intense scrutiny over the tattoo, which he later covered up.

He claimed he was unaware of its resemblance to the Totenkopf — a skull symbol used by Adolf Hitler’s SS troops — until it was highlighted by reporters.

He has also drawn criticism for years-old Reddit posts.

Platner has dismissed the posts as attempts to provoke reactions and said they do not reflect his current views.

Platner is heavily favored to win Maine’s Democratic primary on June 9, setting up a general election challenge against longtime Republican Sen. Susan Collins in a race that could prove pivotal for Senate control.

Auchincloss made clear he will not fall in line for the sake of party unity. “Values and principles always come before party,” he said, comparing the situation to Republicans’ support for Donald Trump in 2016.

The remarks drew swift backlash from the left. Saikat Chakrabarti, a Democratic congressional candidate and former chief of staff to Rep. Alexandria Ocasio-Cortez, accused Auchincloss of effectively endorsing Collins and called for him to be primaried.

Auchincloss defended his stance, describing himself as a “proud Democrat” while pointing to his support for candidates like Texas state Rep. James Talarico, whom he views as better positioned to expand the party’s coalition.