Democrats Begin to Clash Over Who Replaces Platner Even Before He Exits

The implosion of Graham Platner’s campaign for Senate in Maine after an accusation of rape has ripped open divisions inside the Democratic Party as its progressives and moderates battle to pick his successor even before he has said he will step aside.

National Democrats have grown alarmed that a seat seen as crucial to winning control of the Senate could be slipping from the party’s grasp. Mr. Platner had survived a series of controversies — about a tattoo with Nazi symbolism, inflammatory old Reddit posts and his relationships with women — but many in the party abandoned him after the rape accusation, including the leaders of the Maine Democratic Party and Senator Chuck Schumer of New York, the minority leader.

They have demanded that Mr. Platner step down before a July 13 deadline for him to be replaced on the ballot to find a new Democrat to run against Senator Susan Collins, a longtime Republican fixture in the state. The main super PAC for Democratic Senate candidates said it would redirect $24 million in ad reservations to other states if he remained.

Senator Bernie Sanders of Vermont, one of Mr. Platner’s earliest and most prominent backers, joined the chorus on Tuesday afternoon.

“I have spoken with Graham Platner about the best path forward for Maine,” Mr. Sanders said in a statement. “In light of these very serious allegations, I have recommended that he step aside.”

Mr. Platner, who has denied the allegation, said on a private call with his campaign staff on Monday evening that he believed he still had leverage to influence which candidate would replace him on the ticket, according to three people familiar with the conversation. On the call, he did not announce plans to withdraw but implied such a decision would be coming, the people said.