Pro-life demonstrators protest in front of the US Supreme Court in Washington, DC, on January 27, 2017
Washington (AFP) - US anti-abortion advocates have long dreamed of defeating their sworn enemy Roe v. Wade, the Supreme Court decision that enshrines a woman's right to the procedure across all 50 states.
But even with Trump's expected nomination Tuesday of an anti-abortion justice to the Supreme Court, abortion opponents will have inched closer to victory but not yet arrived at a cause for celebration.
The nomination of a conservative to replace deceased justice Antonin Scalia would tilt the court, which is currently divided evenly between four conservative and four liberal justices.
But with conservative justice Anthony Kennedy sometimes joining the progressives when it comes to abortion issues, Trump will have no ironclad assurance on the matter.
Only with the death or resignation of one more justice might Trump be able to stack the court against abortion.
"There is now a serious risk to women's right to abortion, given what Trump has said about his intentions and the likelihood that there will be at least one retirement on the high court in the next four years," Sherry Colb, a professor at Cornell Law School, told AFP.
"If one or more of the five more liberal-on-abortion justices should retire between now and the end of Trump's time in office (whether that be four years or eight years from now), then there would likely be five votes to overrule Roe v. Wade."
Under such a scenario, states would be free to restrict the right to abortion and a Republican Congress could pass national anti-abortion legislation.
On Friday, Vice President Mike Pence hailed the new political era as a "historic" time for the anti-abortion movement.
- Overturn 'unlikely' -
The Roe v. Wade decision was handed down on January 22, 1973, with seven justices backing it and two dissenting.
Now firmly rooted in legal precedent by four decades of doctrine, the ruling will be challenging to completely overthrow.
It is "unlikely that the Supreme Court would overturn Roe v. Wade altogether. But the constitutional right to an abortion would be cut back significantly," said abortion expert Michael Dell.
In a study published this month by the Pew Institute, seven out of 10 Americans are opposed to canceling Roe v Wade. And according to a Quinnipiac survey published Friday, 64 percent of Americans believe that abortion should remain legal, while 31 percent believe the opposite.
Roe v. Wade has had a hectic existence, with its scope diminished by subsequent Supreme Court decisions, and the right to an abortion under constant attack by legislatures in Republican states.
Despite its legality, abortion restrictions take many forms such as bans on certain forms of the procedure, lengthy waiting periods and administrative complications, among other issues.
Under new restrictions, "the gravest impact would be on poor women who lack the resources to travel to where abortion is legal," Colb said.
The Roe v. Wade decision handed down 44 years ago ended a lengthy legal drama that began in the state of Texas three years prior, where abortions were permitted only if the pregnancy endangered the mother or child.
Norma McCorvey, a single mother who had a rough childhood, was pregnant for a third time and wanted an abortion.
Encouraged by two feminist lawyers, McCorvey filed suit under the pseudonym Jane Roe against Dallas district attorney Henry Wade.
Although her child was born, the case took on a life of its own, becoming one of the most important and best-known decisions ever made by the Supreme Court.
McCorvey later became a fervent opponent to abortion, converting to evangelical Protestantism and then Catholicism before eventually coming out as a lesbian.
Trump's announcement for his Supreme Court justice comes after optimistic anti-abortion advocates rallied on Friday in Washington at the 44th annual anti-abortion march, billed as the world's largest "pro-life" rally.