The unlikely new leader of the drive to give vouchers to D.C. schoolchildren is himself a product of Catholic schooling and a politician drawn more to possibilities of experimentation than to the comfort of the tried and true.

A day after stunning much of the city, and much of his staff, by abruptly announcing his support for President Bush's school voucher plan, District Mayor Anthony A. Williams (D) sought to shed more light on what he portrayed as an ideological transformation.

At the root of his new position, he said, was a readiness to try to new approaches to fixing a troubled school system and to offering options to children stuck in bad schools. Over the years, countless parents have begged for more choices, said Williams, who called himself ready to defy his party's orthodoxy to deliver those options.

"We've got a model we've been using for 140 years," he said in an interview. "I think it's time to try something else."

The mayor's record on the public schools has been uneven. Education advocates say that despite funding increases, Williams only intermittently focuses on their issues. He pushed for a charter change allowing him to appoint four of the school board's nine members, but he has left two seats vacant for months. One of his appointees quit after declaring that he couldn't get the mayor to return his phone calls.

Yet aides said that he still regards education as crucial to his legacy as mayor and that he was pleased to put himself at the center of an educational debate -- even if it angered traditional political allies.

It is hardly the first time Williams has clashed with other party leaders. Early in his administration, he seemed to revel in controversy, proposing the school board change, scaling back D.C. General Hospital and suggesting that the University of the District of Columbia be moved east from Northwest Washington to Anacostia.

Just last year, he hosted a fundraiser for Maryland Republican Rep. Constance A. Morella, infuriating Democrats in Congress. D.C. Del. Eleanor Holmes Norton (D) called him "either naive or stupid" for the breach of partisan protocol.

She used even harsher language yesterday, questioning the mayor's commitment to self-government for the city because the voucher idea is an initiative by President Bush and his education secretary, Roderick R. Paige.

Of Williams, Norton said, "He certainly has shown that home rule is not a principle that he holds dear."

But Williams also has allies in his battle, and he certainly will gain more of them if the Bush administration agrees to take on $100 million or more of the city's special education costs, as the mayor has requested.

The push for vouchers is not entirely from the outside. Former D.C. council chairman Sterling Tucker (D) led a group that sought to push a voucher bill through Congress in the mid-1990s. The effort was thwarted mostly by fellow Democrats, including the politically powerful teachers unions.

"Hundreds and hundreds of parents would call us," Tucker said yesterday. "There's no question in my mind how the people feel. People want to get their children the best. . . . They know that's the key that unlocks them out of the ghetto."

Polls consistently show that blacks, particularly those younger than 35, favor new educational choices for their children, even as most African American political leaders oppose vouchers, said David Bositis, an analyst for the Joint Center for Political and Economic Studies, a Washington-based think tank on racial issues. Older blacks, particularly of the civil rights generation, also generally oppose vouchers as an attack on a public school system that long was denied to them.

Bositis said the support for vouchers in polls results mainly from a frustration with poor school systems. "It's more dissatisfaction with the status quo than really support for vouchers," he said.

In predominantly black Ward 7, east of the Anacostia River, D.C. Council member Kevin P. Chavous (D) said there is strong popular support for vouchers, or almost anything else that gives frustrated parents more choices.

Chavous, the head of the council's education committee and another product of a Catholic high school, is a longtime rival of Williams, but the two have reached nearly common ground on the issues after numerous private discussions. The main difference in their positions is that Chavous' support of vouchers is contingent upon public schools also receiving significant aid from the federal government.

Both Chavous and Williams are careful in their public pronouncements about the D.C. public schools, which are responsible for 67,500 students and which would remain the dominant provider of education for the city's youth if vouchers became available. But as they defend their newfound positions, both politicians talk less about the opportunities of private schools than of the hope of getting public schools to pursue their missions more aggressively and creatively.

Williams estimates that the Bush pilot program would aid 5,000 to 10,000 students, but only with enough money to ease their entry to parochial schools, which have modest tuition but limited slots. Most private-school tuitions run in the five figures -- far beyond what is contemplated for the voucher program.

"The really big problem with public education has been its unwillingness to look at itself and change," Chavous said. "No school bureaucracy will reform itself internally. It only comes through pressure. And the most effective form of pressure is choice."

Mayor Anthony A. Williams, top, and D.C. Council member Kevin P. Chavous share increasingly similar positions in support of vouchers.D.C. Del. Eleanor Holmes Norton sharply criticized the mayor's sudden support of school vouchers, saying that "home rule is not a principle that he holds dear."