Conservative members of the Supreme Court on Wednesday leaned toward allowing Oklahoma to approve the first-ever religious public charter school in a case that could weaken the separation of church and state.

While several conservative justices expressed support for the school's arguments, Chief Justice John Roberts emerged during the more than two-hour argument as a potentially decisive vote.

There is the possibility of a 4-4 split, as one justice, conservative Amy Coney Barrett, is not participating. That outcome would preserve an Oklahoma Supreme Court ruling that blocked the proposed school.

Although the oral argument concerned only St. Isidore of Seville Catholic Virtual School, which would operate online throughout the state with a remit to promote the Catholic faith, the case could have broad ramifications.

The dispute, which pits Republicans in Oklahoma against each other, highlights tensions within the Constitution's First Amendment. While the Establishment Clause prohibits state endorsement of religion or preference for one religion over another, the Free Exercise Clause outlaws religious discrimination.

Lawyers for St. Isidore, who are defending the proposal along with the Oklahoma Statewide Charter School Board, have a narrow interpretation of the Establishment Clause and say barring religious entities from applying to run charter schools would run afoul of the Free Exercise Clause.

The Archdiocese of Oklahoma City and the Diocese of Tulsa jointly proposed the school.

In recent years, the Supreme Court has repeatedly strengthened the Free Exercise Clause in cases brought by conservative religious liberty activists, sometimes at the expense of the Establishment Clause. Some conservatives have long complained that the common understanding that the Establishment Clause requires strict separation of church and state is flawed.

Conservative justices expressed doubt that charter schools are public schools that are effectively instruments of the state and favored the school's argument that they are entirely private bodies that just happen to receive state funding.

They also expressed concern that it would be a form of religious discrimination under the Free Exercise Clause to bar religious schools from a state charter school program that other entities can participate in.

"Our cases have made very clear, those are some of the most important cases we've had, saying you can't treat religious people, religious institutions and religious speech as second class in the United States," conservative Justice Brett Kavanaugh said.