San Diego County Supervisor Nathan Fletcher said Thursday that he will resign effective May 15, amid sexual misconduct allegations and a civil lawsuit that have thrown into free fall what had just four days earlier seemed a rising political career.

He plans to remain in office but on medical leave until then, he said, after announcing his plans to resign late Wednesday night. He had said March 26 that he was ending a campaign for state Senate to seek treatment for post-traumatic stress disorder and alcohol abuse.

The Board of Supervisors will decide May 2 whether to appoint a candidate to fill his seat or hold a special election to replace him, county officials said.

Board Chair Nora Vargas did not say which option she will propose for replacing Fletcher, but said she agreed with his decision to resign.

“I’m deeply disturbed by the allegations against Supervisor Fletcher and support his resignation,” Vargas said. “We must work to create a safe environment for all the dedicated people who work throughout San Diego County, and I won’t accept anything less.”

The announcement of his resignation came hours after Fletcher acknowledged inappropriate behavior with Grecia Figueroa, a former Metropolitan Transit System public relations officer who accused Fletcher of kissing and groping her in a lawsuit filed in San Diego Superior Court.

Fletcher denied the assault and harassment allegations but resigned Tuesday from the MTS board, which oversees the San Diego trolley and bus system and which he had chaired.

“The strain on my wife and family over the past week has been immense and unbearable,” Fletcher wrote in a statement late Wednesday night. “A combination of my personal mistakes plus false accusations has created a burden that my family shouldn’t have to bear.”

Fletcher’s initial announcement Sunday had prompted an outpouring of support on social media from constituents and well-wishers who applauded his decision to seek mental health treatment.

But the mood turned critical Wednesday after he acknowledged his interactions with Figueroa.

Supervisor Jim Desmond, a Republican, posted a statement Thursday saying he was “concerned and disappointed by the disturbing allegations of sexual misconduct” against Fletcher, and calling his resignation “a necessary step for the future of San Diego County.”

Board of Supervisors Vice Chair Terra Lawson-Remer did not comment on the allegations or on Fletcher’s resignation, but said in a statement that the board would continue to operate effectively in his absence.

“I have every confidence in our chairwoman and look forward to working with my colleagues to keep delivering for our region,” Lawson-Remer said.

Republican Supervisor Joel Anderson declined to comment.

At least two staffers in his county office resigned Wednesday as a result of the accusations, even though Fletcher broadly denied the allegations in the lawsuit.

Policy director Emily Wier, who had served with Fletcher since 2019, stepped down, as did senior policy advisor Dr. Eric Rafla-Yuan. Both confirmed their resignations but declined to comment.

In his resignation message, Fletcher thanked his supporters and constituents.

“I am proud of what we accomplished together,” he said. “My decision today is solely based on what is best for my family.”

Fletcher’s wife, former state Assemblymember Lorena Gonzalez, registered her support for her husband in a social media post late Wednesday night.

“I love my husband,” Gonzalez said on Twitter. “He has acknowledged his mistakes & I believe his name will be cleared of false accusations. Still, I asked him to resign to lessen the strain on our family.”

Former state Assemblymember Lori Saldaña called for the San Diego County Democratic Party to take action, noting that Fletcher is the second high-profile local Democrat accused of sexual misconduct in just the last year.

Former county party Chair Will Rodriguez-Kennedy stepped down from his position in May after being accused of rape. After an investigation, the district attorney declined to file charges.

Saldaña characterized Fletcher’s behavior toward Figueroa as an “abuse of power” because of his position of authority in the organization.

“When you have a powerful person coercing, expecting, demanding, something from a subordinate, it makes it very difficult for that person to consent without some form of pressure being placed on them,” she said.

Under the party’s bylaws and code of conduct, Central Committee members can be removed for causes including unwelcome advances, retaliation or alcohol or substance abuse, among others, Saldaña noted.

She urged acting party Chair Becca Taylor to ask members to vote on whether to remove Fletcher and Rodriguez-Kennedy from their committee positions.

Taylor said in a statement that she supported Fletcher’s resignation from his county office but did not respond to Saldaña’s request.

Figueroa said in her lawsuit that Fletcher first began interacting with her on social media in 2021. Within several months, she said, he began inviting her to private meetings and kissed and groped her against her will.

She said she was fired from her job at MTS on Feb. 6 — the day Fletcher announced his campaign for state Senate — in what she believes was retaliation.

The transit agency said Figueroa’s termination was “solely related to ongoing performance concerns” and said Fletcher had no role in that decision. It said the board has assigned the labor law firm Paul Plevin Quarles to investigate her allegations.

“None of the decision makers involved in this personnel decision were aware of the allegations about Nathan Fletcher until after the decision to terminate,” the transit agency said in a statement.

“Neither Mr. Fletcher nor any other MTS Board Member was aware of or involved in the decision to terminate Ms. Figueroa.”

No sooner had Fletcher announced plans last month to seek termed-out Sen. Toni Atkins’ state Senate seat than he became the immediate favorite in the race.

But his announcement March 26 that he was ending his campaign, followed by his plan to resign as supervisor, leaves wide open the race not only for Atkins’ Senate seat but also one for the 4th Supervisorial District, which he now represents.

The Board of Supervisors must decide whether to appoint a successor, hold a special election or choose a combination of those options. The board has not indicated how it intends to fill the upcoming vacancy.

The cost and timeline for a special election vary depending on the jurisdiction, the number of registered voters and whether it is an all-mail election or would involve in-person voting, among other factors, San Diego County Registrar of Voters spokesperson Antonia Hutzell said Thursday.

Although the registrar does not have a cost estimate for a special election to replace Fletcher, the most recent special election for the 80th Assembly District — to fill the seat vacated by Gonzalez — cost $2.3 million, Hutzell said.

Potential candidates are already throwing their names in the hat for Fletcher’s seat.

Amy Reichert, who lost a challenge to Fletcher in November, is considering a second run.

“I do hope there is a special election,” Reichert said Thursday. “I think the people deserve to vote for their elected representative. I am absolutely interested in running for county Board of Supervisors.”

Veterans advocate Janessa Goldbeck had previously announced plans to run for Fletcher’s open seat should he be elected to the state Senate but said Thursday she’s prepared either to run for the seat or to apply for an appointment now.

“This obviously changes the timeline, but I’m not deterred; I’m doubling down,” Goldbeck said Thursday, calling Fletcher’s behavior “deeply disturbing and disappointing.

“As a former victims advocate, I fought for the rights of men and women who were victimized by people in positions of power. And now more than ever I think San Diego County needs leadership that truly lives up to our values.”

Brennan and McDonald write for the San Diego Union-Tribune. Staff writer Kristen Taketa of the Union-Tribune contributed to this report.