WASHINGTON —The Supreme Court challenge to a Texas law that has dramatically reduced the number of abortion clinics in the state is the justices’ most significant case on the hot-button issue in nearly a quarter-century.

One of this election-year term’s biggest cases is being argued Wednesday before a court altered by the death of Justice Antonin Scalia. He was perhaps the most vociferous abortion opponent among the nine justices.

The Texas law has been replicated across the South and elsewhere, part of a wave of state abortion restrictions in the past five years.

States mainly led by Republicans have tried to limit when in a pregnancy abortions may be performed, restricted abortion-inducing drugs that take the place of surgery and increased standards for clinics and the doctors who work in them.

The Supreme Court case involves that last category. A Texas law enacted in 2013 requires doctors who perform abortions to have admitting privileges at nearby hospitals. It also prohibits clinics from providing abortions unless they meet the standards of outpatient or ambulatory surgical centers.

The high court has partially blocked those measures. If allowed to take full effect, all but 10 clinics in Texas would have to close. There would be no abortion providers in the state’s rural areas or west of San Antonio. The only clinic in the Rio Grande Valley would be allowed to remain open on a limited basis. Before the law was passed, there were roughly 40 clinics in the state. About half have closed.

The case offers competing views of how to protect women’s health. The clinics contend abortions are safer than many other medical procedures that are less stringently regulated and that the clinic regulations have only one purpose: to reduce the availability of abortions.

“These laws are tantamount to an outright ban for too many,” said Amy Hagstrom Miller, chief executive of Whole Woman’s Health, which operates clinics in Texas and other states.

Defenders of the laws in Texas and elsewhere argue that states have discretion to take steps to make abortions safer. Alabama and other states backing Texas told the Supreme Court that states were within their rights to apply health regulations to clinics for the sake of patients.

Texas Solicitor General Scott Keller, who will defend the law at the Supreme Court, said Texas acted in response to the high-profile case of Philadelphia abortion doctor Kermit Gosnell. He is serving a life sentence after his conviction for killing three babies born alive and for the overdose death of a woman who was a clinic patient.

A federal judge in Texas struck down parts of the law as not intended to promote women’s health and clearly aimed at reducing access to abortion.