With Washington bracing for the battle over who will fill the Supreme Court seat being vacated by retiring Justice Anthony Kennedy, pro-life groups see an opening to overturn the 1973 Roe v. Wade court decision that legalized abortion nationwide, a reversal that could bring the debates over abortion back to the states.

“Justice Kennedy’s retirement from the Supreme Court marks a pivotal moment for the fight to ensure every unborn child is welcomed and protected under the law,” Marjorie Dannenfelser, president of the Susan B. Anthony List, said in a statement on Wednesday.

Though Mr. Kennedy was appointed by a Republican, President Ronald Reagan, he tended to side with the more liberal wing of the court on so-called social issues, including same-sex marriage and abortion.

“I believe we will end abortion, and ensuring that the next Supreme Court justice is pro-life is the best way to start.”

The president of Americans United for Life said in a statement that she hopes President Trump will appoint a justice who could swing the court toward upholding laws restricting abortion. With Mr. Kennedy’s retirement, Catherine Glenn Foster said, her group urges President Trump “to nominate a committed constitutionalist to the Supreme Court who will hew to the intended meaning of the nation’s charter and refrain from employing it as a means of social engineering.”

The Rev. Frank Pavone, the head of Priests for Life, took to Twitter to urge his followers to “join with us in what could be the battle of our lifetimes.”

“I believe we will end abortion, and ensuring that the next Supreme Court justice is pro-life is the best way to start,” Father Pavone wrote, adding that he hopes for “a consistently pro-life justice to be nominated and confirmed to the Court.”

Mr. Trump, who signed a letter this week to anti-abortion activists meeting in Kansas in which he said he is “dedicated to protecting the lives of every American, including the unborn,” told reporters on Wednesday that he would choose his nominee from a list of 25 names the White House released last November in anticipation of possible Supreme Court vacancies.

The reported frontrunner on that list is Brett M. Kavanaugh, a federal appellate court judge for the District of Columbia Circuit who once clerked for Mr. Kennedy. Like Justice Neil Gorsuch, who was added to the Supreme Court in 2017, Mr. Kavanaugh completed high school at the Jesuit-run Georgetown Prep School. Mr. Kavanaugh, who is Catholic, later graduated from Yale Law School, worked on the special counsel investigation of President Bill Clinton and served as a staff secretary to President George W. Bush.

The reported frontrunner is Brett M. Kavanaugh, a federal appellate court judge for the District of Columbia Circuit who once clerked for Mr. Kennedy.

According to his official biography, Mr. Kavanaugh volunteers with Catholic Charities, tutors at a D.C. Jesuit middle school and is a parishioner at Blessed Sacrament Catholic Church in Washington.

Another name under consideration is Amy Coney Barrett, a federal judge who was previously a law professor at the University of Notre Dame. Ms. Coney Barrett made headlines last year when, during her confirmation hearing as a federal judge, questions from some senators drew accusations of anti-Catholic bias.

Writing at Bloomberg, columnist Ramesh Ponnuru urged the president to select Ms. Coney Barrett, writing, “She is the youngest of the five top choices, which is a mark in her favor given that the nominee will have life tenure and Trump will want one who will leave a lasting mark on the law.”

Mr. Ponnuru speculated that Ms. Coney Barrett would support overturning Roe vs. Wade and wrote that such a reversal “would be better if it were not done by only male justices, with every female justice in dissent.”

Overturning Roe, long a goal of pro-life organizations, would not ban abortion. Instead, it would allow states to regulate the practice. Before Roe was decided, 17 states allowed abortion in some cases. Following the decision, all 50 states were required to legalize abortion.

Mr. Ponnuru said that overturning Roe vs. Wade “would be better if it were not done by only male justices, with every female justice in dissent.”

Other names reportedly on Mr. Trump’s short list include Amul R. Thapar, a federal judge in Kentucky; Raymond Kethledge, a federal judge in Michigan; and Thomas M. Hardiman, a federal judge in Pennsylvania.

Kristen Day, head of Democrats for Life, told America, “We have to prepare for a post Roe v. Wade world and we’re not there yet. We have a lot more work to do.”

She said that Democrats who oppose abortion are in a “precarious” situation when it comes to considering judicial appointments. While a conservative nominee may align with some pro-life goals, he or she could rule against other policies important to both progressives and pro-life activists.

Even if Mr. Trump appoints a justice with pro-life views, some say it is not a guarantee that Roe will be overturned.

“Liberals should be less despondent—and conservatives should be less giddy—about Justice Kennedy’s retirement,” wrote David Lat, the editor of the legal-affairs website Above the Law. “This time next year—or the year after that, or the year after that—things won’t be that different. We won’t be living in a nation where abortion, gay marriage, and affirmative action are all illegal by June 2019—or June 2020, or June 2021. There might be some changes at the margins, but nothing fundamental.”

Mr. Lat wrote that he believes Chief Justice John Roberts will work to preserve the court’s reputation by avoiding any dramatic decision on abortion or gay marriage, which was legalized nationwide by the court in 2015.

“Chief Justice Roberts is an institutionalist who guards the credibility and political capital of the Court closely; he would surely want to avoid the unfathomably bitter, nationwide controversy that overruling Roe would create,” Mr. Lat wrote, though he conceded the court may “shift a bit to the right on abortion.”

Charlie Camosy, an ethicist at Fordham University who opposes abortion, offered a similar prediction on Twitter.

“Pro-lifers of a certain age remember the last time Republicans got enough judges to overturn Roe. They gave us PP v Casey,” Mr. Camosy tweeted on Thursday, referring to the 1992 case in which Mr. Kennedy surprised court watchers by reaffirming the validity of Roe.

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“I worry about Roberts, frankly,” Mr. Camosy wrote. “He might be the next Kennedy.”

Michael J. O’Loughlin is the executive editor and C.E.O. of National Catholic Reporter. Previously he was the national correspondent at America. He is also the author of Hidden Mercy: AIDS, Catholics, and the Untold Stories of Compassion in the Face of Fear.