U.S. Sen. Debbie Stabenow, D-Mich., added her voice to those in the Senate calling for Sen. Al Franken, D-Minn., to resign in the face of mounting accusations of sexual harassment and molestation.

Stabenow posted on Twitter on Wednesday morning, "Sexual harassment is unacceptable. I believe Senator Franken should do the right thing and resign."

By midday, some 14 other members of the U.S. Senate — including at least nine women — had issued calls for Franken to step down, rather than remain in office while an ethics investigation is ongoing.

Franken's office has said the senator would make a statement on Thursday.

The accusations against him began some weeks ago, when a woman said he forcibly kissed her and pretended to grope her before he entered Congress and the two were on a USO trip overseas.

Since then, several other allegations have been leveled at him, including the most recent accusation in which the Washington, D.C., publication Politico cited an unnamed Democratic congressional aide who said Franken cornered her in a studio in 2006 and forcibly tried to kiss her.

Franken — who had a long career as a comedian, writer and radio host before entering the U.S. Senate — has apologized to the women who have come forward while saying he did not intend to harass or molest anyone. He has also promised to cooperate with the ethics investigation.

He expressly denied the most recent allegation in Politico, however.

The calls for Franken's resignation come in the immediate aftermath of U.S. Rep. John Conyers' retirement on Tuesday after numerous accusations were raised against him by former staff. Conyers, D-Detroit, denied the accusations, but stepped down saying he could not receive due process in the current environment in Washington.

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