Richard Wolf

USA TODAY

WASHINGTON — President-elect Donald Trump opposes abortion, but even he admits that overturning the Supreme Court's 43-year-old decision in Roe v. Wade "has a long, long way to go."

After Trump nominates a justice to replace the late Antonin Scalia, the Supreme Court will remain one or two votes short of a majority to send abortion decisions back to the states, experts on both sides of the issue agree.

There are several reasons: The high court does not like to overrule its own precedents, particularly those that have stood for decades and affected millions of people. When it does, it tends to do so incrementally, which could mean allowing states to impose more restrictions on abortion without eliminating the federal right entirely.

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Then there is the issue of who sits on the court and how strongly they feel about abortion. Though Justice Clarence Thomas and whoever Trump selects might be ready to jettison Roe, neither Chief Justice John Roberts nor Justice Samuel Alito is committed to doing so. Roberts, in particular, is an incrementalist who has the court's reputation as an institution to consider. For that reason, Trump might need to replace two more justices to make a difference.

"There's a long road ahead and many obstacles," says Clarke Forsythe, acting president and senior counsel at Americans United for Life. Even if the court eventually reverses itself, he says, "the issue would go back to the states, most of whom have repealed their pre-Roe prohibitions."

Nancy Northup, president of the Center for Reproductive Rights, says a few states such as Louisiana, Mississippi and North and South Dakota have abortion bans ready to implement if the Supreme Court acts. Her group says 21 states are likely to ban abortion almost immediately, and 20 others — including California, Florida and New York — are likely to preserve abortion rights. Nine others would be "battlegrounds."

"We would be faced with a pretty challenging landscape," Northup says. “People would have to cross many state lines … to be able to get access to safe and legal abortion.”

The Supreme Court's 7-2 decision in Roe balanced a woman's right to have an abortion against the desire of some states to protect the unborn by allowing increased levels of regulation during the last trimester of pregnancy. Two decades later in Planned Parenthood v. Casey, the court upheld that basic right but allowed more limits based on the viability of the fetus.

Justice Samuel Alito's replacement of Justice Sandra Day O'Connor led the court in 2007 to uphold a federal law banning late-term, or "partial birth," abortions. After Scalia's death this year, the court voted 5-3 against a Texas law that imposed harsh requirements on abortion clinics and doctors who perform abortions.

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Those five justices — Anthony Kennedy, Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan — remain on the court. To move toward a reversal of Roe would require one or more of them to leave while Trump is president.

If the court remains closely divided but with five justices opposed to abortion, most analysts predict it will move slowly — perhaps by upholding state restrictions greater than those allowed under Casey — before deciding whether to overturn its 1973 decision. "You could shut down most abortion clinics without overturning Roe," says Neal Devins, a law professor at William & Mary Law School who has written on the subject. The Texas law struck down in June would have forced all but nine clinics statewide to shut their doors.

James Bopp, general counsel for the National Right to Life Committee since 1978, says the past four decades have seen several occasions where it seemed federal abortion rights were at risk, only to be salvaged. The most important thing about Trump's election, he says, is that Hillary Clinton would have nominated a sixth Supreme Court justice who favors abortion rights.

“That bullet was avoided," Bopp says, but Scalia's replacement won't lead to a reversal of Roe v. Wade. "It's more than one (justice) away," he said. "There's no question about that."