WASHINGTON — Sen. Heidi Heitkamp, D-N.D., called for the resignation of Sen. Al Franken, D-Minn., on Wednesday, joining the morning surge of Democrats who began demanding Franken step down after reports of a seventh woman accusing him of inappropriate conduct.

“We must commit to zero tolerance,” Heitkamp wrote on Twitter. “Which is where I believe we as a country and Congress should be — and that means Senator Franken should step down.”

Heitkamp’s statement was posted shortly after a wave of Democratic senators began calling for Franken to step down. Shortly before noon, there were 13 lawmakers asking Franken to resign, as well as Tom Perez, the chairman of the Democratic National Committee.

On Wednesday morning, Politico published claims from a former Democratic aide that Franken had tried to forcibly kiss her in 2006. It’s the seventh account of inappropriate conduct that has been published in the past weeks since radio host Leeann Tweeden said Franken kissed and groped her without her consent.

“I’ve said before that for decades as a country, we have been far too tolerant and dismissive of past allegations,” Heitkamp said in her Twitter statement. “In recent months, women have been courageously stepping out of the shadows to tell their stories of sexual harassment and abuse. That’s a huge step. We need to stand by them and all women to empower them to come forward and speak out, prevent those actions, and impose serious consequences when they do happen.”

Heitkamp’s office did not immediately answer emailed questions about the timing of her call for Franken’s resignation.

Franken plans a Thursday announcement in Washington. Although details were not forthcoming, the consensus was that he would resign.

Franken apparently has not been in Minnesota since Nov. 11, days earlier than allegations began to be reported a week before Thanksgiving. He talked to some Minnesota reporters and stopped to talk to Washington media last week before heading to his first Senate meeting after the first allegation surfaced.

The senator largely has been silent in public in recent weeks.