The school voucher movement appeared to be on its way to a major constitutional victory before the U.S. Supreme Court Wednesday.

During oral arguments in an Ohio case considered crucial to the future of voucher programs nationwide, key swing Justice Sandra Day O'Connor appeared largely untroubled by the argument that taxpayer-funded vouchers, as they operate in Cleveland, overwhelmingly benefit religious schools. Under the program, poor students can use state vouchers worth $2,250 to pay for private school tuition as an alternative to public schools.

Even though 99 percent of the Cleveland students using vouchers attend religious schools, O'Connor suggested repeatedly that the benefit to religion is much less pronounced when the voucher program is considered together with traditional government funding for public and charter schools as well as for tutoring in the public schools.

"Do we not have to look at all the choices?" when evaluating the constitutional question, O'Connor asked at one point.

Though post-argument predictions were hard to come by in Zelman v. Simmons-Harris, No. 00-1751, it appeared that if O'Connor votes in favor of vouchers, she would seal at least a five-vote majority.

"The arguments went very, very well," leading voucher advocate Clint Bolick told more than 100 cheering demonstrators in front of the Court, just moments after the 80-minute hearing. Bolick, vice president of the Washington, D.C.-based Institute for Justice, did not argue himself.

The trio of lawyers who did argue in support of the voucher program -- Ohio Assistant Attorney General Judith French, private practitioner David Young, and U.S. Solicitor General Theodore Olson -- made a seamless presentation that appeared to calm some of the concerns expressed by justices over the church-state issue.

French assured the Court that the voucher program was neutral -- available to all students depending only on income and residence -- and that no money passed to religious institutions without the "true private choice" of parents.

Justice John Paul Stevens countered that parental choice was part of the parochial aid program the Court struck down nearly 30 years ago in the landmark case Committee for Public Education & Religious Liberty v. Nyquist.

"It's the same case," Stevens said.

But French and Young distinguished the cases by noting that the Cleveland voucher program includes money for tutoring that goes to public schools and is also open to suburban public schools.

Justice Stephen Breyer suggested that the program would give someone "from Africa or Europe" the impression that "a very large amount of money is being paid to parochial schools."

But Young, partner in the Columbus, Ohio, office of Cleveland's Squire, Sanders & Dempsey, insisted "there is no government endorsement" because so many other tax dollars go to public schools. "The preference is clearly for the secular schools," Young said.

Olson bolstered the point, describing the Cleveland plan as a "pilot program, an experimental program" initiated because of a "manifestly failing system" of public education. He also suggested that the program may not always have the same heavy concentration of religious schools that it now does. Under Milwaukee's voucher program, not before the Court, the number of nonreligious schools has been rising, Olson said.

Robert Chanin, the main anti-voucher advocate, ran into trouble with O'Connor almost immediately. She had already signaled that the Cleveland program should not be viewed in isolation, but Chanin did so anyway, saying that as the program has evolved, it is a "mathematical certainty" that taxpayer money will go to sectarian schools.

When O'Connor challenged him to take the broader view, Chanin said the Court has always looked at individual programs when deciding whether they violate the establishment clause of the First Amendment.

"You ask us to put on blinders," said Justice Anthony Kennedy.

"We are asking you to look at the reality," countered Chanin, general counsel of the National Education Association.

"Part of the reality," corrected Kennedy.

As Chanin proceeded, his passionate presentation bordered on a harangue, with his voice rising as he waved an angry finger at the justices. Vouchers are a "lousy option" for curing the problems of Cleveland schools, he said with disgust. "I don't think a crisis in Cleveland schools is a license to ignore" the First Amendment, Chanin added.

Asked if the constitutional balance would change if only 50 percent of the voucher students went to parochial schools, Chanin snapped, "Not in my mind." Eventually he conceded that if only one of 100 voucher students went to a religious school, his objections would not be as strong.

But Chanin continued to resist the analysis offered by O'Connor. "So far you are doing a very good job of not answering Justice O'Connor's questions," said Kennedy at one point.

Rehnquist also became exasperated, telling Chanin he had clearly not answered the Court's concerns satisfactorily. When Chanin started to respond, interrupting Rehnquist, the chief justice's face began to redden.

Chanin backed off, saying he did not mean to interrupt Rehnquist. "You better not," Rehnquist said sharply.

The argument ended on another unusual note, with retired federal judge Marvin Frankel arguing against vouchers from a seated position. Frankel, 81, a longtime expert on church-state issues and a partner in New York's Kramer Levin Naftalis & Frankel, was recently hospitalized.

In contrast to Chanin's aggressive style, Frankel spoke almost too softly. He sought to place the voucher issue in a different context, viewing it as a diversion from Ohio's statewide efforts to correct inequities in school funding.

Rehnquist and Scalia politely suggested that Frankel's argument was not relevant to the establishment clause issue before the Court.

Frankel said his points were raised in the lower courts but "slipped by them," and he continued reviewing the history of the school funding issue until his time was up.