Hundreds of thousands of abortion-rights advocates streamed down Washington's main streets yesterday for a march and rally that organizers said was a powerful show of strength in a year that they fear the U.S. Supreme Court will restrict a woman's right to abortion.

The March for Women's Lives, which police said drew 500,000 people, was one of the largest political events in the city's history. It attracted dozens of congressional candidates, a couple of presidential hopefuls and thousands of marchers who promised to get involved in local, state and national campaigns.

Dianne Feinstein, former San Francisco mayor and now a Senate candidate, roused the crowd to a roar shortly before the march began when she, flanked by nearly a dozen other abortion-rights candidates on a stage near the Ellipse, called for rallies beyond Washington.

"Are you willing to work and {walk the} precincts and get people to vote for pro-choice candidates?" Feinstein asked. "I hope today begins a series of marches . . . throughout the United States" to support abortion-rights candidates.

The march organizers, the National Organization for Women and dozens of other groups, were jubilant about the turnout. They estimated that 1 million people participated, twice as many as the official estimate of U.S. Park Police and D.C. police.

The demonstration that jammed Pennsylvania Avenue for four hours was peaceful but spirited. There were a few shouting matches along the route between some marchers and small groups of antiabortion demonstrators, and a three-hour counter-demonstration on the west lawn of the U.S. Capitol drew about 200 people. U.S. Park Police intervened in some standoffs and arrested one person on a charge of vandalism near the White House.

This election year has energized both sides of the abortion issue. The Supreme Court is weighing a case that could restrict its 1973 ruling in Roe v. Wade that established a constitutional right to abortion. The case, which challenges a Pennsylvania law that restricts abortion, could be decided in July and play a role in the national election.

NOW President Patricia Ireland said the march showed abortion rights will be a significant issue this fall and in future elections. "For our friends, the message is we are going to be there for them," she said.

"The other message is that we are going forward from this place to recruit far more women for office. We are not looking to make any more compromises. We want the real thing now. We want women we can believe in with our whole hearts. And there's a whole lot of women getting ready to run."

Ireland said NOW and its supporters have been working for months to generate voter interest and that helped the march. Phone banks were set up and teams of organizers promoted the march on more than 600 college, high school and junior high campuses, she said.

NOW also mailed out requests for help and networked with welfare, poverty and homeless groups, she said. In addition, NOW reached out to small pools of supporters, Ireland said.

A call would come from a campus with 600 people wanting to march, she said. Others called with a bridge club of women who wanted to come. One woman went to a bar mitzvah and organized her family in a delegation. A junior high student from McLean decided to have her birthday party at the rally.

"Obviously, we have the mechanisms in place to get out the vote," Ireland said.

Yesterday's march began under cool, sunny skies shortly after noon and ended as the hundreds of thousands of people filled the parkland between the U.S. Capitol and the Washington Monument.

The famous and familiar were at the forefront: author Gloria Steinem, actress Jane Fonda, Ireland, D.C. Del. Eleanor Holmes Norton, D.C. statehood lobbyist Jesse L. Jackson, and former New York representative Bella Abzug in a white straw hat.

Behind them were people who had hopped on the Metro from Arlington; car pooled from Philadelphia; ridden buses from Columbus, Ohio; taken an early Amtrak train from New York and jetted in from Chicago, Orange County, Calif., Boston and Key West, Fla. They were students. They were housewives. They were accountants, lawyers, office workers, Roman Catholics, Jews, Protestants, heterosexual and homosexual, predominantly white. About half were under 30.

Some had marched on Washington before. Some had never done anything like this.

"This is just the beginning," said Elna Brossman, 22, of Arlington. "I'd definitely like to do more, anything to get more active. . . . You've got to get out and speak up or you can't complain about how our country is being led."

Brossman, a zookeeper at the National Zoo, said it was her first march. She came for personal, as well as political reasons: One of her friends had an abortion. "It really hit close to home," she said. "It was a very hard period to go through. At least she could get it taken care of."

There were more women than men, but together they chanted along the march route, carried placards, shared bags of pretzels and other munchies and, when they finally made it to the Mall, stretched out on the grass to hear speeches.

"Women will never be equal to men unless they have control over their bodies," said Perry Flint, 34, who was caring for his 4 1/2-month-old son. "The point of the rally is to send a message to the president and Congress and the Supreme Court, that far more people feel it's important for women to have that control.

"George Bush makes me pretty mad," Flint added. "I voted for {him} four years ago and really regret it."

Jill Cichosky, 24, a therapist from Philadelphia, said all her friends had been talking about the march and she had to come. She has had two legal abortions herself, she said.

The mood was "very affirming," she said. "Sometimes you feel very alone on this issue. Now I don't. Because there are a million people out there saying, 'Yes, you are not alone.' "

Every conceivable affiliation of supporter seemed to bond for this rally -- or at least had a banner to wave: B'nai B'rith for Choice, Republicans for Choice, Clergy for Choice, Southern Women for Choice, Blue Devils for Choice (with a small nod to the NCAA men's basketball Final Four) and, perhaps a bit wistfully, Menopausal Women Nostalgic for Choice.

"It's the first I've marched for reproductive rights," said Alejandro Reuss, a 21-year-old who was marching with a group of students from Harvard University. "I think if you care for women's rights, you have to be here."

Antiabortion activists held steadfast in their belief that abortion murders the unborn. "Not NOW! Not NOW!" they chanted in a peaceful counter-demonstration, organized by the Feminists for Life, outside the Capitol.

"NOW, you don't represent me. NOW doesn't represent the majority of opinion of the women of America," said Jessica Crossed, one of the organizers.

In addition to the Capitol lawn demonstration, members of Operation Rescue, which blockaded an abortion clinic in Southeast Washington on Saturday, used bullhorns to chide the abortion-rights demonstrators. U.S. Park Police asked leader Randall Terry and a handful of others to leave one confrontation at a morning prayer service for abortion-rights supporters.

If politics was the purpose behind yesterday's rally, many in the crowd found their time well spent. Illinois Democrat Carol Moseley Braun, fresh from an unexpected primary victory, drew enthusiastic applause.

Democrat Paul Tsongas, who is considering reentering the presidential race, showed up without notice at the front of the march and a cheer went up. Democratic contenders Bill Clinton and Edmund G. "Jerry" Brown Jr. also attended the rally and were met with sign-waving supporters, although neither was allowed to address the throng from the podium.

Yesterday's march attracted the most people ever to an abortion-rights rally and ranks as one of the largest demonstrations in the District. In 1989, police estimated 300,000 came for a similar gathering. In November 1969, the Vietnam Moratorium Day drew 600,000.

Last year, 800,000 people turned out for a parade and victory celebration for Desert Storm. The largest crowd on record in Washington was 1.2 million in 1965 for the inauguration of President Johnson.

Staff writers Nell Henderson, Carlos Sanchez and Paul Valentine and editorial assistant Gagan Nirula contributed to this report.