-- Hundreds of thousands of antiwar protesters, abortion rights supporters, labor rights activists and anarchists are preparing to unfurl banners, march through the streets and rally in the parks, loosening a cacophonous roar of protest during the Republican National Convention.

As many as 250,000 people may march up Seventh Avenue by Madison Square Garden on the Sunday before the convention to protest the war in Iraq. Thousands of abortion rights and women's health advocates plan to walk across the Brooklyn Bridge to City Hall Park. And the Hip Hop Summit Action Network will lead a march of low-income people to Madison Square Garden, the convention site.

That's not to mention the Paul Revere impersonators who plan nightly horseback rides down Lexington Avenue in Midtown (their warning cry: "The Republicans are coming! The Republicans are coming!"). Or the bell ringers who plan to encircle Ground Zero and ring 2,749 bells in memory of the victims of Sept. 11, 2001, and in opposition to the Iraq war.

Or Cheri Honkala, a welfare mother from Philadelphia, who says she expects to bring in 5,000 rural and urban folks for a purposefully illegal march across town to Times Square. "The police told us there was no way in hell they were going to give us a permit to march," she said. Honkala, who led a similar march at the Republican convention in Philadelphia in 2000, shrugged. "We have to mess it all up. . . . Poor people have been living with terror every day."

New York has a proudly oppositional DNA -- Democrats outnumber Republicans 5 to 1 -- so protests come as no surprise. But at a time of terrorism alerts and deep liberal unhappiness with President Bush, the Aug. 30-Sept. 2 convention will test the government's ability to secure the safety of delegates while allowing hundreds of thousands of Americans to raise a constitutionally protected voice of dissent, civil libertarians and city officials say.

This is a test, activists say, that several city and state governments have failed. In Miami, for instance, a county review panel found that police had instituted martial law and trampled the civil rights of protesters during a free-trade conference last November. In Georgia, county officials mandated small protest signs and state police kept protesters miles removed from the Group of Eight summit at Sea Island.

Boston officials, too, came under criticism for herding protesters at the Democratic National Convention into fenced pens.

"Dissent is a cornerstone of a democratic society," said Norman Siegel, former director of the New York Civil Liberties Union. "It's how we measure whether we're an open society, and it's under a lot of stress now."

Tension is already evident. Marches will proceed under the eyes of a massive police, FBI and Secret Service presence, as more than 10,000 local officers will patrol the barricaded streets around the convention. Undercover police have infiltrated meetings of anarchist groups, and prosecutors are ready to process as many as 1,000 arrests per day.

The FBI acknowledged Monday -- after a report in the New York Times -- that agents have interviewed potential demonstrators across the nation. In some cases, protesters say they were asked about their political views. FBI officials insisted their agents conducted interviews only after learning of people planning disruptions at the conventions.

"The FBI conducted interviews, within the bounds of the U.S. Constitution, in order to determine the validity of the threat information," said FBI Assistant Director Cassandra M. Chandler.

Antiwar organizers here knew of no one who had been interviewed. But such interviews, they said, seemed intended to chill dissent. The National Lawyers Guild intends to distribute cards advising activists to say nothing if the FBI knocks. "It's a chilling reminder of the world we live in," said Tanya Mayo of Not in Our Name, an antiwar group.

Organizers of marches large and small complain of uncommon difficulty in obtaining permits from the city. The largest of the planned antiwar marches still has no terminus. Organizers with United for Peace and Justice, representing more than 100 antiwar, religious and social justice groups, sought to march through Midtown to a rally in Central Park on Aug. 29, the Sunday before the convention. Parks Department officials rejected this.

"You'll ruin the lawn," Republican Mayor Michael R. Bloomberg said.

In a Jupiter-aligned-with-Mars-moment, the conservative New York Post and the liberal New York Times editorial boards both took up the protesters' cause. But, reluctantly, organizers accepted an alternate site along Manhattan's West Side Highway, only to reject it again last week after rank-and-file activists howled in anger. They said a long strip of concrete in midsummer makes for a hot and dispiriting protest site and is no substitute for Central Park, which has far greater symbolic value.

"We are under a constant pressure to give up freedom in the face of fear," said Bill Dobbs, an organizer with United for Peace and Justice.

City officials take strong exception to this. They have worked hard, they say, to ensure that legal protests will snake through Manhattan's office canyons. They speak of learning from mistakes and will not so tightly pen in protesters, as occurred at a large antiwar demonstration in February 2003.

"We're working to give them a large piece of city territory to stage protests," said Deputy Police Commissioner Paul J. Browne. "We've devoted a lot of resources and worked very hard to allow unfettered free speech despite the fear of terrorism."

Browne noted that the New York Police Department has traveled a long road since the anti-Vietnam War protests, when cops would show up in riot gear with no desire to compromise. "There was no conversation at all, and that didn't help anybody," Browne said, adding that the current department has posted directions to large protests on its Web site. "Now there's negotiation, but that opens some groups up to charges they are being co-opted."

The Parks Department has granted permits for 16 rallies in Manhattan parks, ranging in size from 20 people to 40,000. But officials recently denied a permit to the National Council of Arab Americans and the Act Now to Stop War and End Racism Coalition, a group that wanted to rally with 75,000 people on the Great Lawn, just below the official capacity of 80,000. These groups are suing.

To a large extent, police say, large rallies are easiest to handle. These demonstrations tend to be carefully choreographed, with experienced organizers and channeled, if genuine, outrage. The greater challenge, for police and organizers alike, is to handle the hundreds of decentralized protests that will pop up around the city.

Just last week, one found a provocatively named singing group in Times Square performing satirical and not exceptionally nice songs about Bush. Then there's Reverend Billy, who leads his flock from the Church of Stop Shopping about the city reciting the First Amendment into their cell phones. And a group of labor activists plan to stage the world's longest unemployment line, from Wall Street to 31st Street and Madison Square Garden, on Sept. 1. The line will form at 8:13 a.m. and dissolve at 8:31 a.m.

The Yippies stand amid such protesters as wiseacre elders. They applied for a camping permit for 20,000 people in Tompkins Square Park -- denied instantly. As a backup, they want to set up tables with free medical marijuana for bedraggled police officers, a kindness that seems no less doomed to rejection.

Then there are the anarchist collectives, a free-floating catchall term that incorporates hundreds of young activists, tattooed train hoppers and nomads. Their rhetoric is thick with talk of police states. The Web site, www.rncnotwelcome.org, includes detailed maps of surveillance cameras in Manhattan and lists of hotels housing Republican delegates. There are detailed instructions on the best public bathrooms and the best places to shoot heroin, not to mention lessons in the art of tossing a pie.

"Pieing 101: Step One, Choose a worthy target," the Web site advises. "Any pompous evil-doer will do."

The "hacktivist" wing of the anarchists wants to get wiggy with RNC Web sites. Others have already sneaked into Republican events and plastered revolutionary stickers on bathroom walls. Half a dozen groups plan to block streets peacefully. The Web site advises the proper anarchist to "dress for success," in a ski mask and a good pair of running shoes.

Deputy Commissioner Browne acknowledges that police will keep a close eye on the black-ski-mask set. In other cities, such as Seattle and Miami, police were accused of too brutal a pursuit. He promised that would not happen in New York.

"We would expect the real radical anarchists to number in the hundreds," he said. "We're familiar with them, and we're prepared to isolate them from the mass of peaceful protesters if necessary."

Siegel, the civil liberties lawyer, feels less certain. He has cautioned city officials that, by denying permits to many established groups and forcing others from Central Park, the department has engendered a distrust that could haunt it.

"Now the climate is so hostile, that when there are splinter groups or unplanned actions, the trust that's needed won't be there," Siegel said. "The present atmosphere in the nation is not conducive to trust."

Demonstrators aren't waiting for the Republican convention. At a block party in protest of the Bush administration last week in Brooklyn, performer Rasp Thorne depicts the American flag as a noose.