SACRAMENTO, Calif. — A third Democratic California assemblyman announced Wednesday that he is resigning, citing health reasons.

The departure of Sebastian Ridley-Thomas further whittles down the Democratic majority in the Assembly after two of his colleagues announced in the last month that they are leaving amid sexual misconduct complaints.

Ridley-Thomas said in a statement that he has undergone five surgeries this year, the most recent on Dec. 18, and expects to fully recover from a condition he didn’t specify.

However, his doctors say he needs an extended time to recuperate.

Holding office and running for re-election next year “involves constant travel, an unrelenting schedule and high stress,” he said. “Unfortunately, at this point, I am no longer able to deliver the effort my constituents in the 54th District deserve.”

He said he intends to remain active in civic affairs.

Thomas, 30, grew up in a politically connected Los Angeles family, winning his seat at 26 in a special election in 2013. He is the son of Los Angeles County Supervisor Mark Ridley-Thomas.

Assembly Speaker Anthony Rendon said in a statement that the Assembly will assist Ridley-Thomas’ constituents until his seat is filled. The Los Angeles-area district includes Baldwin Hills, Crenshaw, Culver City and Westwood.

Gov. Jerry Brown will set a date for a special election to replace Ridley-Thomas.

The resignation, effective Sunday, leaves Democrats with 52 of the Assembly’s 80 members, two votes short of what once had been a two-thirds supermajority.

Democrats expect to retain the seat now held by Ridley-Thomas.

Supermajorities were needed this year to pass a gas tax increase and reauthorize the cap-and-trade pollution program.

An April 3 special election is set to replace former Assemblyman Raul Bocanegra, who resigned last month amid sexual misconduct allegations. If no candidate wins at least 50 percent of the vote, a general election will take place June 5, the same day as the statewide primary.

Bocanegra said in a statement last month that he is “not guilty of any such crimes.”

A date hasn’t been set to replace Assemblyman Matt Dababneh, another San Fernando Valley Democrat, who plans to resign Jan. 1. He denies a lobbyist’s allegation that he assaulted her in a bar bathroom last year.

Jimmy Gomez also left the Assembly this year when he was elected to Congress. He was recently replaced by Democrat Wendy Carrillo of Los Angeles.