President Obama’s nomination of Elena Kagan to the US Supreme Court represents a turning point in American religious history: If Kagan, who is Jewish, is confirmed, the high court will not have a single Protestant member.

More than half of all Americans are Protestant, while less than one-quarter are Catholic and just 1.7 percent are Jewish, according to the US Religious Landscape Survey by the Pew Forum on Religion and Public Life. But, if Kagan is confirmed to the bench, the nation’s highest court, dominated by Protestants for most of its history, will be made up of six Catholics and three Jews.

“This whole project of a Protestant America is really going under, and it’s going under quickly,’’ said Stephen Prothero, a professor of religion at Boston University and author of “God is Not One: The Eight Rival Religions that Run the World — and Why Their Differences Matter.’’

Kagan’s nomination, he said, “is an important moment of saying, ‘Look, we’ve gone so far beyond the idea that this is a Protestant country that we can have a court with six Catholics and three Jews.’’

Martin E. Marty, professor emeritus at the University of Chicago Divinity School, said that these days, the question of whether there should be a distinctly Protestant voice on the court would elicit “a big yawn’’ from most mainline Protestants.

“I was in an Episcopal church in Chicago on Sunday, and there were a lot of movers and shakers there, but we didn’t sit around after and say, ‘How can we get one of us on the Supreme Court?’ ’’ he said.

Evangelical Protestants have been slow to embrace or to feel welcomed by elite law schools like Harvard and Yale that have become a veritable requirement for Supreme Court nominees.

One reason for this, some scholars say, is an anti-intellectual strain within evangelicalism.

“Evangelical Christianity has tended to be a populist religion that’s strongly democratic, in urging people to read the Bible themselves,’’ said Mark A. Noll, a history professor at the University of Notre Dame. “All these are traits that have positive sides, but not for intellectual preparation and education.’’

But Noll and others say this is changing. Like Catholics and Jews of the last century, evangelicals are increasingly realizing that they need intellectual credentials to acquire institutional power in America.

Influencing the high court is of special importance to evangelicals because of their opposition to abortion.

“I think the Catholics had a 20-year head start on the . . . evangelicals in getting more elite credentials,’’ said Richard W. Garnett, a professor of law at the University of Notre Dame.

A half-century ago, Catholics and Jews were the outsiders in the top echelons of the legal and political worlds.

But barriers to their advancement have now largely disintegrated, as both groups have made significant strides in educational and professional achievement.

“Education itself became important, with a kind of edge that was not present for most Protestant groups,’’ Noll said.

Republican presidents, seeking Supreme Court nominees with strong educational credentials who oppose abortion rights, have in recent years turned repeatedly to Catholics.

“It’s not that every Catholic justice is prolife, obviously,’’ Garnett said. “But if you were looking for a qualified candidate with elite credentials who was prolife in the ’80s, ’90s, and early 2000s, you were likely to find a lot of Catholics.’’

Evangelicals sometimes view Catholics as their ideological soul mates, so President George W. Bush could please his political base by nominating Samuel Alito after his first choice, evangelical Harriet Miers, withdrew from consideration over criticism that she was ill prepared.

“There was a time that being fearful of Catholics was at the heart of Protestant culture; that’s certainly changed,’’ said David Harrington Watt, a history professor at Temple University.

Democratic presidents, seeking Supreme Court nominees who are reliably liberal, have several times nominated Jewish justices.

President Clinton appointed both of the court’s current Jewish justices, Stephen Breyer and Ruth Bader Ginsburg.

Some scholars lament the lack of religious diversity on the court.

“We think through ethics and law in our lives, whether we are Supreme Court justices or not, in light of our backgrounds and religious commitments,’’ Prothero said. “And I think it’s a pity to have only two religious traditions represented on the court.’’

Lisa Wangsness can be reached at lwangsness@globe.com.

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