San Francisco ? Slapped down by California’s Supreme Court, Mayor Gavin Newsom remained defiant in his quest to make same-sex marriages legal.

He immediately approved a new constitutional challenge, predicting that his view will ultimately prevail.

“I hope every elected official in the United States takes a look at that Constitution that they swore to uphold,” he told a crowd at City Hall, where his brazen move allowed 4,000 gay and lesbian couples to wed.

“I hope they conclude exactly what I’ve concluded — that there’s nothing in the Constitution that allows me to discriminate against people.”

Whether Newsom, 36, is ahead of his time or has doomed his political future, he clearly has fired up a national debate already simmering after Massachusetts’s highest court declared gay marriage legal there. Scores of gay couples have since wed in other cities that have followed San Francisco’s lead, including about 2,000 in Portland, Ore.

All this from a mayor who had been in office less than two weeks when he decided to thrust the city into the center of the nation’s culture wars.

Newsom was considered to be about as conservative as politicians come in San Francisco, narrowly winning a December runoff against a popular Green Party candidate.

He claims the decision to allow gay marriage — which caused his approval ratings to soar to 65 percent among city voters — was made without political calculation.

“Guys like me come and go,” he said in an interview with The Associated Press. “The one thing that transcends everything else are principles. If I just wanted to get ahead politically, this issue is the last issue I would have touched.”

Most prominent Democrats were initially shocked into retreat as gays and lesbians lined up outside City Hall. Some criticized the weddings as a self-conscious vanity crusade on behalf of the country’s most gay-friendly city that would set back gay rights efforts elsewhere.

But Newsom didn’t back down, even after President Bush cited the San Francisco wedding spree as a key reason for endorsing a constitutional amendment banning same sex marriage. The straight, Catholic, married mayor went on national television and became a principal antagonist in the fight over family values.

“This is a revolution within society, and sometimes it takes a young leader to take the courageous step,” said California Democratic Party Chairman Art Torres. “I admire him, I think the world of him, and I will do everything I can to assure his future in the Democratic Party.”

But the move could prove politically challenging for other Democrats, said Leon Panetta, the chief of staff for President Clinton.

“The general rule in politics is don’t make waves, and most people in office feel generally this type of wedge issue has lots of dangerous aspects to it,” Panetta said.

Even if the city loses the next court battle, it has already succeeded in putting a human face on the debate, demonstrating that “you can’t deal with discrimination in the abstract,” Newsom said at a St. Patrick’s Day reception Friday.

“That is what I believe we have achieved,” he said. “There is nothing a court can do, a politician can do, to take away the last 29 days and what we have done in San Francisco.”