Rep. John Conyers Jr. (D-Mich.) said he was retiring on Dec. 5, after facing multiple sexual harassment allegations spanning two decades. He endorsed his son to replace him. (Jenny Starrs,Joyce Koh/The Washington Post)

Facing multiple allegations of sexual harassment, Rep. John Conyers Jr. (D-Mich.) resigned as Congress’s longest-serving member Tuesday, becoming the first lawmaker to step down as Capitol Hill grapples with allegations of inappropriate behavior by lawmakers.

Conyers, who represented the Detroit area for 52 years, yielded to mounting pressure from Democratic leaders to step aside as a growing number of female former aides accused him of unwanted advances and mistreatment. He has denied wrongdoing.

From a hospital in Detroit, the 88-year-old congressman said he was “putting his retirement plans together” and endorsed his son John Conyers III to replace him. Another Conyers family member has already declared his intention to run for the seat, raising the specter of an intrafamily contest.

Asked about the harassment allegations, Conyers said his legacy “can’t be compromised or diminished in any way by what we’re going through now.”

“This, too, shall pass,” Conyers told a local radio station in an interview. “My legacy will continue through my children.”

Conyers’s abrupt departure marks the end of a career that spanned the Watergate hearings, impeachment proceedings against President Bill Clinton, the Afghanistan and Iraq wars, and the debate over a national health-care system. Conyers influenced debates over each issue as a member and, eventually, as chairman of the powerful House Judiciary Committee. He recently stepped aside as the panel’s ranking Democrat.

Conyers is hospitalized for what his lawyer has described as a stress-related illness. His family has not provided further details.

Described by supporters as an icon of liberal policymaking, Conyers was revered on Capitol Hill as a founding member of the Congressional Black Caucus. The group declined last week to call for his resignation, pitting its members against House Minority Leader Nancy Pelosi (D-Calif.), who said that he must leave Congress.

Conyers’s resignation comes as his colleagues grapple with how to address the growing public outcry over sexual harassment on Capitol Hill, which some female lawmakers and aides have described as rampant. Disclosure of a $27,000 settlement Conyers reached with a former employee intensified scrutiny of Congress for its secretive system of settling harassment complains.

Sen. Al Franken (D-Minn.) is facing multiple allegations of inappropriate touching. He has apologized, and he suggested in a recent statement that any unwanted touching was not intentional.

Rep. Blake Farenthold (R-Tex.) said Monday that he would reimburse taxpayers after it was revealed that he used $84,000 in public funds to settle a sexual harassment complaint. He has denied wrongdoing.

And Pelosi called on Rep. Ruben Kihuen (D-Nev.) to resign after his former finance director alleged that he made unwanted advances toward her on the campaign trail. Kihuen, who has not denied the allegations, apologized for any comments or actions that made the staffer “uncomfortable.”

In a statement Tuesday, Pelosi said Conyers’s accusers “were owed the justice” of his resignation. She called for the House to approve legislation reforming the system for filing and settling workplace complaints on Capitol Hill.

“Congressman Conyers has served in the Congress for more than five decades, and shaped some of the most consequential legislation of the last half century. But no matter how great the legacy, it is no license to harass or discriminate,” she stated.

Now that Conyers has resigned, Michigan Gov. Rick Snyder (R) will call a special election to replace him that could pit two Conyers family members against each other.

The grandson of Conyers’s brother indicated Tuesday that he plans to run. Ian Conyers, a Michigan state senator, wrote on Twitter on Tuesday: “I look forward to our local and national media taking a thorough look at all candidates to replace my uncle @RepJohnConyers.”

He did not respond to messages seeking comment.

Less is known about John Conyers III, the retired congressman’s preferred successor and his son with former Detroit City Council member Monica Conyers. A writer and aspiring rapper, he is described as a “partner at Detroit’s first minority run hedge fund” and a “seasoned multi-discipline consultant” on his contributor page at the HuffPost.

He has defended his father in several media interviews as more women emerged to accuse Conyers of misconduct.

“It’s disconcerting to me to see the way my father is being treated after he’s given so much to this country — not just for black people but for people alike. He fights for everyone,” John Conyers III told local reporters last week.

Snyder’s office confirmed that it received Conyers’s official letter of resignation and now can begin reviewing possible election dates.

Outside the Conyers home, longtime Detroit political consultant Sam Riddle said it is not clear that either John Conyers III or Ian Conyers will win the seat.

“We are on the verge of the biggest free-for-all politically you’ve ever seen in Detroit,” Riddle said at a news conference. “There should not be an automatic ascension to that congressional seat because your last name is Conyers.”

Black activists continued to defend Conyers, arguing that “white hypocrites and phony liberals” found it easier to call for his resignation than Franken’s because Conyers is African American.

“You’re going to catch pure hell, Democratic Party, getting out the vote in Detroit,” Riddle said.

Conyers’s legacy was a complicating factor for his colleagues as they weighed their responses to the misconduct allegations.

In 1964, when he won his first term, Conyers was one of just five black members of Congress. He hired Rosa Parks, who served on his staff until her retirement in 1988, and backed the major planks of President Lyndon B. Johnson’s “Great Society” program, including the Voting Rights Act.

In April 1968, four days after the assassination of the Rev. Martin Luther King Jr., Conyers introduced the first bill proposing a holiday in honor of the civil rights icon. As a member of the Judiciary Committee, he made a successful push for impeachment proceedings against President Richard M. Nixon.

In recent years, Conyers lent his name and clout to several progressive bills, not least the Expanded and Improved Medicare For All Act. In 2017, a majority of Democrats — for the first time — co-sponsored the measure, putting them on the record for universal health care.

Rep. Raúl M. Grijalva (D-Ariz.), a longtime co-chairman of the House Progressive Caucus, said the Conyers-backed bills — which had no chance of passage in this Congress — would be adopted by other members. “People can pick up the load,” he said.

In and out of the House majority, Conyers established himself as a fierce critic of Republican policies. During the George W. Bush administration, he held unofficial hearings to challenge the results of the 2004 election and to investigate whether the Iraq War had been launched under false pretenses.

While in Congress, Conyers ran twice for mayor of Detroit, but lost both bids in the Democratic primary. He had more success on Capitol Hill, where he took over as chairman of the House Oversight Committee in 1989. Six years later, he became the top Democrat on the Judiciary Committee, a role he held until late last month.

Conyers’s decision to step aside comes as Congress struggles to explain its secretive process for investigating and settling claims about sexual harassment and other workplace misconduct.

Under a system created more than 20 years ago, victims must undergo counseling and mediation before they can pursue legal action against members who mistreat them. Settlements are paid out of a special Treasury Department fund, designated for the purpose, or out of members’ office budgets.

Conyers paid a former employee in 2015 out of his own budget after she made a sexual harassment complaint, listing the payment as severance, according to House payroll records. He has denied wrongdoing in the case.

“We take these in stride,” he said Tuesday of the harassment accusations. “This goes with the issue of politics, the game of politics which we’re in.”

A previous version of this story incorrectly referred to Conyers as the first African American congressman to represent Detroit. It was Charles Diggs.

Mike DeBonis in Washington and Steve Friess in Detroit contributed to this report.