California lawmakers place a constitutional amendment protecting abortion rights on the fall ballot.

SACRAMENTO — California state lawmakers on Monday put a state constitutional amendment on the ballot that would explicitly protect reproductive rights, moving swiftly on the first business day after the Supreme Court reversed Roe v. Wade.

The amendment, which will go to California voters in November for approval, comes as abortion rights groups across the country react to the sweeping decision ending longstanding abortion protections. It comes after Vermont leaders earlier this year agreed to put a constitutional guarantee before voters in that state.

At least 15 states and the District of Columbia affirmed or expanded abortion rights before Friday’s court shift, while roughly two dozen other states signaled that they would end or dramatically restrict access to the procedure.

On Friday, Gov. Gavin Newsom of California signed a bill to shield California abortion providers from liability or prosecution related to out-of-state bans on abortions. He also announced an agreement with Gov. Kate Brown of Oregon and Gov. Jay Inslee of Washington to establish a West Coast abortion firewall that would protect providers and patients from the legal reach of other states.

California’s Constitution already includes a right to privacy that has long underpinned abortion statutes. But after the Supreme Court leak in May, the state’s legislative leaders moved to make certain that abortion and contraception are explicitly protected.

The amendment “would make it undeniably clear that in California, abortion and contraception are health care and are a private matter between a patient and their medical provider,” explained Toni G. Atkins, the president pro tempore of the State Senate, who directed a women’s health clinic in San Diego before entering public service.

The Senate previously passed the amendment with supermajority approval, and it needed to receive at least two-thirds support in the Assembly by this week to go before voters in November. The amendment did not require Mr. Newsom’s signature to qualify, but he supports it.

“Abortion bans do not end abortion,” Anthony Rendon, the Assembly Speaker, said shortly before the chamber, which is dominated by Democrats, overwhelmingly approved the measure. “They only outlaw safe abortions.”

The 58-16 vote came largely along party lines, with several Democratic legislators sharing personal experiences in which abortion rights shaped their lives and expanded their — or their mothers’ — options, and Republican legislators stressing moral and religious considerations and medical advances that have shifted the point at which a fetus can live outside the womb.

“My twin boys are alive and they are people,” said James Gallagher, a Republican Assembly member and father of four from rural Yuba City, Calif. “And they were alive and they were people at 18 weeks when doctors at U.C.S.F. were preparing to perform surgery on their hearts in utero.”

Opponents also include the California Catholic Conference, which has criticized the proposal’s wording as “extreme” and so loose that it could be interpreted as allowing late-term abortions.

“The sad reality is that California already has some of the most accommodating abortion laws and services in the nation,” the conference said in a statement, vowing to muster “the state’s 12 million Catholics” in its fight against the amendment.