But legal documents published by BuzzFeed show repeated allegations by female staff members of requests for sex, suggestive touching, caresses and other sexual improprieties. On Tuesday evening, BuzzFeed wrote about a separate lawsuit against Mr. Conyers filed in February in the United States District Court for the District of Columbia, later withdrawn after the court denied the accuser’s motion to seal the proceedings.

In the suit, a former scheduler for Mr. Conyers said she suffered through unwanted touching and romantic advances “repeatedly and daily” in 2015 and 2016.

The calls for an investigation came as Democrats privately raised the prospect that Mr. Conyers would at least be asked to step aside from the coveted top Judiciary post. Mr. Conyers, a founding member of the Congressional Black Caucus, also holds the venerated title of Dean of the House. But he has been a target of Democrats who are eager to bring fresh blood into the Judiciary Committee leadership for some time, three congressional officials said.

He has already handed over much of the day-to-day committee work to staff aides and other Democratic members in recent years, and has often appeared disoriented. In at least two separate occasions — once at a United Automobile Workers event in Michigan and once at a meeting of top Democrats on Capitol Hill — Mr. Conyers showed up wearing pajamas, according to two people familiar with the incidents.

A spokeswoman for Mr. Conyers said she had “no knowledge this ever occurred.”

On Tuesday, some House Democrats viewed the charges as an opening to finally remove him.

“The allegations against Ranking Member Conyers are extremely serious and deeply troubling,” said Representative Jerrold Nadler of New York, the second most senior Democrat on the Judiciary Committee. “There can be no tolerance for behavior that subjects women to the kind of conduct alleged.”

A group of Democrats from across the caucus had pushed for such a move at the start of the year, but were beaten back by Mr. Conyers and allied lawmakers, according to House Democrats familiar with the matter. Since then, they said, it has been commonly understood that this term would be Mr. Conyers’s last atop the committee.