Seattle Mayor Ed Murray (D), facing multiple child sex-abuse allegations dating to the 1970s, will resign Wednesday, saying the damaging claims have become a distraction that threatens to undermine the city government’s ability to serve its citizens.

Murray’s spokesman, William Lemke, told The Washington Post the resignation takes effect at 5 p.m.

The announcement Tuesday came just hours after the Seattle Times reported new allegations Murray, 62, sexually abused a relative in the mid-70s. That relative, a cousin, was the fifth man to publicly accuse the mayor of sexual assault, the newspaper reported.

Murray continues to deny the accusations, saying his progressive political record and gay-rights advocacy made him a target for those determined to drag him down. His cousin’s allegations, Murray told the Times, stem from “bad blood between two estranged wings of the family.”

In a written statement issued by the mayor’s office, Murray said, “While the allegations against me are not true, it is important that my personal issues do not affect the ability of our City government to conduct the public’s business. … It is best for the city if I step aside. To the people of this special city and to my dedicated staff, I am sorry for this painful situation.”

Elected mayor in 2013, Murray dropped his reelection bid in May after the first four men claimed he had sexually abused them years earlier, when they were teenagers. One filed a lawsuit in April, alleging in lurid detail Murray “repeatedly criminally raped and molested” him when he was a homeless 15-year-old in the 1980s.

The other alleged victims chose not to sue.

Murray resisted calls to resign, a decision some members of the Seattle City Council supported before his cousin’s allegations surfaced this week. As recently as June, when the lawsuit was withdrawn, Murray even suggested he’d run again as a write-in candidate, saying he felt vindicated.

Seattle is home to nearly 715,000 people and one of the nation’s fastest-growing economies, fueled in large part by the tech boom and steady expansion by several major firms headquartered there.

City Council President Bruce Harrell will step in to serve as mayor. Seattle’s charter gives him five days to decide whether to remain through the rest of Murray’s term, Harrell announced in a statement.

“I have a plan in place for a seamless transition in order for City operations to continue at the highest standard,” Harrell’s statement said. “Seattleites deserve a government that holds their full confidence and trust.”

Harrell called the accusations against Murray “unspeakable,” saying the city’s criminal justice and social service systems have an obligation to address them “no matter how long ago they might have occurred.”

Murray, who was raised in Seattle, became a campaign manager for Washington’s first openly gay state senator in the 1980s. He went on to serve for nearly two decades in the state legislature, where he prioritized transportation measures, gay rights and marriage equality.

Murray continued to champion social justice issues while at city hall, winning the mayor’s seat in part with a promise to raise the minimum wage to $15 an hour, which he accomplished through an executive order not long after his election.

He took on affordable-housing challenges and police accountability and would become one of President Trump’s harshest critics on the West Coast, particularly the administration’s promise to target undocumented immigrants.

Speaking on the condition of anonymity to offer a frank assessment of Tuesday’s announcement, a source in Seattle City Hall told The Post Murray’s resignation has left many in the government feeling “deflated.”

The mayor’s staff was in the midst of finalizing next year’s budget, pursuing an ambitious agenda — on issues from homelessness to preschool — with the goal of cementing Murray’s legacy as a public servant.

“There was still work to be done,” the source said. “And there are a lot of questions about how this will play out.”

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