SAN FRANCISCO -- On an unseasonably warm Saturday, the biggest demonstration in years packed the downtown streets of this famously liberal city, voicing angry opposition to the Bush administration's plans to invade Iraq. Coming just weeks before most observers expect the Bush administration to launch its attack, the demonstration, along with the huge march in Washington, D.C., and many smaller protests around the country, was intended to send a loud message to the White House that many Americans are strongly opposed to its coming war.

And, this being the Bay Area, they also sent the message that they are even more strongly opposed to Bush himself.

As always, the exact size of the protest was a subject of dispute. In one of those absurd estimates that give credence to left-wing paranoia theories that local authorities are taking their marching orders from Attorney General Ashcroft, police estimated the size of the march at 55,000. I'm no professional crowd estimator, but I've been to plenty of games at Candlestick Park (football capacity: 60,000) and the idea that a sellout crowd there would completely fill four-lane Market Street all the way from the Ferry Building, on the Bay, to the Civic Center, about two miles away, is patently ridiculous. Organizers claimed the real figure was closer to 200,000. A veteran San Francisco policeman said it was the largest march he had witnessed in two decades.

San Francisco has always provided the Dadaist flavor to the American left (New York City's anti-shopping guru "Rev. Billy," Bill Talen, cut his teeth in the performance scene here) and Saturday's protesters did not disappoint. On the corner of Front and Market, a sinister Uncle Sam on stilts cackled as he poured a can of gasoline down the craw of a man costumed as a grotesque Bush, a rolled dollar bill shoved up his nose for youthful-indiscretion purposes. A pale, frightened-looking woman on stilts dressed as the Statue of Liberty cowered next to Uncle Sam, chained to a lamppost. "Drink up, buddy!" loudly exulted Uncle Sam as the reeling, arm-waving Bush chug-a-lugged the unleaded. "That's what makes him strong!"

Turning to the crowd, Uncle Sam bellowed to nearby cops, "Arrest all these people!" He shook his fists and screamed, "I hate this city! Why can't you be normal Americans! Buy, buy, buy! Kill, kill, kill!"

Extreme fear and loathing of Bush was a common theme of the day's signs, banners, T-shirts, speeches and conversations. "Dear Florida, thanks for the war -- Love, SF," read one sign. Other expressions of distaste ranged from the time-honored sign "Regime Change Begins at Home" to "Emperor Bush -- You Do Not Represent Me" to "Georgy Porgy Pudding and Pie/Bombing the People and Making Them Die" to "End Bush's Evil Regime" to "George Bush: Weapon of Mass Destruction" to "Born to Kill, Born to Drill" (accompanied by a photo of Bush as Rambo) to the somewhat crude but undeniably straightforward "Bullying Unilateralist Shithead."

At a booth in the Civic Center, next to a sign reading "Antiwar magazines" was another reading "Anti-Bush Magazines -- $1, $2, and $3." Sales appeared brisk.

Considerable creative energy went into some attacks on the president. One large one read "Stop the Fourth Reich -- Visualize Nuremberg/ Iraq." On the other side were rows of doctored photos of all the top-ranking Bush administration officials wearing Nazi uniforms and officers' caps, each with an identifying caption. Bush was identified as "The Angry Puppet" and Mind-controlled Slave/ 'Pro-life' Executioner." Cheney: "The Fuhrer, Already in His Bunker." Powell: "House Negro -- Fakes Left, Moves Right." Rice: "Will Kill Africans for Oil." Ashcroft: "Faith-based fascist, sexless sadist." "Field Marshall Rummy," "Chickenhawk Wolfowitz -- Jews for Genocide," and "Minister of Dis-info -- Ari Goebbels" rounded out the field.

As the march crossed scuzzy 6th Street, a scruffy young guy walked along, wearing a sandwich board with a photo of President Bush reading "Have Some More Pretzels, Bush (Fucker)." He had attempted to kick the sophomoric humor up a notch by gluing several dozen pretzels to the sign.

Another man wore a shirt bearing one of those Bush-is-a-moron images constantly disseminated on the Internet, showing the commander in chief looking through a pair of binoculars that still had the lens caps on. The sign read "Follow Him Blindly? Hell No!"

Signs carried by many other protesters, however, took a mellower approach. "We Are Americans -- We Don't Kill Children." "Let's Sit and Talk." "An Eye for an Eye Makes the Whole World Blind." And there were a few old chestnuts from the flower power age: "Give Peace a Chance," "War Is Unhealthy for Children and Other Living Things," "Make Love, not War."

Still others were more substantive. "Unprovoked Invasion of Any Country Is Evil. Iraq 2003 = Poland 1939. Thousands Will Be Killed, Billions Will Be Spent Because a Few People Are Obsessed With One Man."

There was quirky wit. "How Did Our Oil Get Under Their Sand?" And the historically informed: "At least Caligula Gave Rome the Whole Horse!"

And, of course, there were the only-in-S.F. sentiments: big costumed figures of Trickster Coyote and a Native American woman, adorned with a sign reading "Arms Are For Hugging." A woman wearing a T-shirt reading "Just Another Jewish Lesbian Who Says No to War," another woman carrying a sign reading "The Only Bush I Trust Is My Own." And the totally inexplicable "Pirates Against the Warrrgh," carried by a teenage girl.

The Civic Center was unable to accommodate the vast throng. Much of the crowd dissipated after getting there -- which may have led to the low police estimate -- but tens of thousands of people remained for a rally featuring performances by Joan Baez and Bonnie Raitt and speeches by a number of politicians and celebrities, including actor and longtime activist Martin Sheen. ("You know what I do for a living, but this is what I do to stay alive!" Sheen, who plays the president on the TV show "The West Wing," boomed to the crowd.) The march took place on the eve of the Martin Luther King national holiday, and many speakers invoked the Rev. King's name and legacy. Rep. Barbara Lee, D-Calif., who immediately after the 9/11 attacks cast the lone dissenting vote against giving Bush unlimited power to pursue the war on terror, roused the crowd, thanking them for "watching my back" and invoking King as she denounced the "real axis of evil -- poverty, racism and war."

The march, organized by a group called ANSWER (Act Now to Stop War and End Racism), drew people from Los Angeles, Sacramento and even farther away. Some protesters were attending their first peace march. A broad spectrum of the Bay Area was represented -- members of labor unions, vets, teachers, and self-described "Parents against the war" rubbed shoulders with students and activists. But if it was a diverse and mainstream crowd by the standards of San Francisco political protests, it was still an unruly and unholy mob of weirdos by Middle American standards. Regiment after regiment of the Bay Area's finest passed (there is something atavistic and ironic in the way that protests conjure up images of troops on parade) and although there were many straight-looking families and yuppies and respectable-looking older people, the S.F. army was dominated by a familiar blend of non-letter-sweater-wearing students, gaunt, Nietzsche-reading bikers, feisty free-spirit grannies, weird nebbishes for Latin American liberation, kinky capitalists, violent pacifists, immortal bards of Mission District coffee houses, middle-aged, Birkenstock-wearing professors, clear-eyed, middle-class Left Coast people of deep spiritual inclinations, and so on. There were quite a few black people, some Latinos and Asians, and a fair number of Arabs. Many keffiyehs were in evidence; one young white guy was draped in a Palestinian flag.

But this wealthy region's more genteel lefties also showed up. Grace Cathedral, atop swanky Nob Hill, hosted an 11 a.m. rally of environmentalists against the war, who then descended down Hyde Street in a flotilla of hybrids and electric and alternative cars. A woman in a Toyota Prius said there were 40 people in her group. Bumper stickers read "Go Solar, not Ballistic," "Real Patriots Drive Hybrids" and "If War Is Inevitable, Start Drafting SUV Drivers Now." A long-haired guy stood on the corner of Bush Street as the endless procession drove past, holding up a sign that read "Don't Blame Me -- I Voted With the Majority."

Later, down at the bottom of the Hyde Street hill at the Civic Center, a therapist attending the rally with his teenage daughter quipped, "When the environmentalists met the rest of the march, it was like the elves joining up with the dwarves."

A handful of counterdemonstrators stood on the steps of City Hall, holding signs that read "Leftists Hate America," "Blessed Are the Peacemakers -- U.S. Army, Navy, Air Force, Marines," "Liberate the People of Iraq," "Have You Forgotten 9/11 -- Justice For the Victims" and "Saddam Pays Homicide Bombers." They were confronted by a small group of protestErs, but nothing stronger than verbal abuse ensued. (The day was peaceful until the end, when 200 black-clad demonstrators went on a rampage in the financial district, smashing the window of a Starbucks coffee shop, spray-painting antiwar messages on the Citicorp building and vandalizing the Immigration and Naturalization Service building. )

A group of seven or eight Arabs, men, women and children, were standing near a fence in Civic Center; several were wearing keffiyahs. A young woman named Amani Morrar said she and her family were from Palestine. "But I was born here," she said. Her family was from Ramallah, in the West Bank. She was 23 years old, lived in the working-class South Bay city of Fremont and was a student at Chabot Community College. She was here with her family. ("I go to CSUS," a male relative proudly interjected.)

Why was she opposed to the war? She looked like she could barely believe she was being asked the question. "I'm opposed to the war because as a Palestinian we know how it is," she said. Did she think that part of Bush's plan in invading Iraq was to strengthen the Israelis at the expense of the Palestinians? "Of course," she said. "It isn't just Iraq -- they want to take over the rest of the Arab countries, like Syria. This is just the start."

Did she think the war could result in Arab anger that would lead to more acts of terrorism against the United States? She thought, then nodded. "It's the only way they're being heard," she said.

Past a loud group of drummers, past whiffs of patchouli oil, past a group of 60 or 70 people meditating with eyes closed, past the booth run by the Socialist Worker's Party, past the "Free Mumia!" banners, three young women walked along, adorned with signs reading "Another Waitress for Peace" and "Waiters and Bartenders for Peace." Rachel Herndon, 21, was a bartender at the Caffe Mediterraneum in Berkeley, a famous grad-student haunt on Telegraph Avenue. Amy Gerber, 27, was a waitress there, as was Page Heimsoth, 24. They said most of their friends were waitresses and bartenders and a lot of them were getting involved in the antiwar movement. "Next time we want to come in our aprons and take people's orders and send them to Bush," said Gerber. Was this their first march against the war? "No -- we've gone to all of them."

Asked why she opposed the war, Herndon's eyes flashed and her words tumbled out. "It's completely corrupt; it's going to cause so much reciprocal violence. It's corrupt because it's not about nuclear arms -- Pakistan and North Korea have them and we don't care. It's about power, and it involves racism and hatred toward Islam. We're heading toward fascism."

Gerber said, "I oppose any military action in the Middle East now. We're ignoring the Palestine issue, while we're dropping bombs on a country that has been suffering under our sanctions for -- what is it --12 years."

Heimsoth said, "It seems like a perpetual problem; our going to war is so hypocritical."

Were any of them troubled by the Bush administration's argument that Saddam was too dangerous a leader to be allowed to have weapons of mass destruction -- that he might pass them on to terrorists or use them against our allies?

They all snorted derisively. "Look at North Korea," Herndon said. "I'm embarrassed every time I see our leaders talk about this. In light of North Korea, I'm actually embarrassed. All around the world, people are outraged by this. They can't believe we're preparing to go to war.

"I just got out of college," she said, "and this is the world I have to deal with."

One elderly couple ambled through the Civic Center, the man holding up a sign that read "Republicans Against the War," the woman one that read "Patriots for Peace." Their names were Bob Barton and Ellen Floyd; he was 70, she was 75. They lived in Marin County. Did he vote for Bush? "No. We didn't vote for him because by the time the election came we realized he was lying," Barton said. "He said he was a 'compassionate conservative,' and that turned out to be a lie. We're real conservatives -- we want to conserve the environment, conserve the Constitution. But he's given the party away to the radical right-wing, the religious right. That isn't conservatism."

Why did they oppose the Iraq war?

"I don't think we're in serious enough danger to warrant a war," Barton said. "They're trying to connect it to 9/11. 9/11 was a criminal act, but not an act of war. So I support hunting those people down, but you can't have a war on terror. You can't make war on an abstraction."

"I oppose all war," Floyd said.

"The only possible justification for war is self-defense," Barton went on. "And with Iraq, that's a stretch. There isn't enough evidence. And a preemptive strike is un-American."

It turned out that Barton's sign was a bit misleading. He wasn't a registered Republican anymore; in fact, the last time he voted for a Republican was Richard Nixon. But in San Francisco, on this day, that put him somewhere to the right of Genghis Khan.