Jake Auchincloss

Rep. Jake Auchincloss, D-Mass., is breaking ranks with his own party ahead of Maine's pivotal Senate race, refusing to support Democrat Graham Platner over a tattoo controversy and the candidate's past inflammatory comments online.

"I've been clear about Graham Platner. I find that tattoo and his commentary about it to be personally disqualifying," Auchincloss told CNN on Monday. "I hope Maine voters agree with me."

The Massachusetts congressman, who is Jewish, warned Democrats against embracing what he called Platner's version of the party.

"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," Auchincloss added.

Platner — a progressive Democrat, Army veteran and oyster farmer — has faced mounting scrutiny after critics pointed to a tattoo on his chest resembling the Totenkopf, a skull insignia historically associated with Nazi forces.

After backlash erupted, Platner said he had the tattoo covered and claimed he did not know about the symbol's Nazi connection until it was flagged by "reporters and D.C. insiders."

"I absolutely would not have gone through life having this on my chest if I knew that — and to insinuate that I did is disgusting. I am already planning to get this removed," Platner said last October.

Platner has also come under fire for old Reddit posts in which he referred to himself as a "communist" and called police officers "bastards."

During an appearance on "Pod Save America" podcast, Platner attempted to distance himself from the remarks, saying the posts were intended to "get a rise out of people."

Despite the controversies, Platner is still widely expected to win Maine's Democrat primary on June 9 and move on to challenge moderate Republican Sen. Susan Collins in November.

When CNN asked whether he could support Platner in the general election, Auchincloss declined to endorse him.

"Values and principles always come before party," Auchincloss said.

"We saw Republicans forget that lesson with Donald Trump in 2016 and how much damage it's done to the country," he continued. "I will never forget that lesson."

The comments drew backlash from progressive Democrats, including Saikat Chakrabarti — the former chief of staff to Rep. Alexandria Ocasio-Cortez, D-N.Y. — who accused Auchincloss of effectively helping Collins hold the seat.

"Jake Auchincloss is essentially endorsing Susan Collins in Maine," Chakrabarti wrote on social media Monday. "Absolutely no excuse for a Democrat in the House to back a Republican for Senate in a crucial swing seat."

"Auchincloss should be primaried," he added.