At 10 o'clock Sunday morning, when I joined the crowd that two hours later would begin a protest march past Madison Square Garden, the Republican National Convention site, I felt good about how the day was starting.

Seventh Avenue, the main route of the march, was already filling up, and the crowd, which would reach 400,000 by some estimates, was cheerful despite a temperature already in the 80s. Most people were in shorts, and the smell of suntan lotion was everywhere.

Predicting what a protest crowd, especially a New York protest crowd, will do is never easy. But I find it helpful to ask three questions: Does the crowd have diversity and a visible component of marchers over 50? Do the marchers feel deeply enough about their cause to make homemade signs? Do the parents in the march bring their children with them?

If the answer to all three questions is yes, as it was on Sunday, then I think a protest march has a good chance for success. It rests on a solid base. What worries me these days about big marches is that it is easy for "the crazies" to take them over by provoking confrontations that upstage the march.

That almost happened on Sunday. A handful of demonstrators set a paper dragon on fire in front of Madison Square Garden. A right-wing group, ProtestWarrior.com, which, as its Web site boasts, makes a point of crashing liberal demonstrations, came close to starting a couple of fights. And after the march was over, a splinter group blocked the entrances to two midtown hotels and tied up late-afternoon traffic.

That these provocations did not succeed and that a small protest on the Great Lawn in Central Park remained peaceful, was, I think, a sign not only of how politically savvy Sunday's crowd was, but of its awareness that these days most mass demonstrations are political theater. They do not change the opposition so much as encourage those who share the protesters' views to work harder because they believe their numbers give them a chance for success.

The catch is that for the political theater of a protest to bear fruit, the protest must also be inclusive. In the case of Sunday's protest, there had to be room for people who oppose Bush on a variety of fronts, as well as for people (myself included) who want him defeated but who are made uneasy by the caricature of him as stupid. (For instance, I see nothing silly about once believing that Saddam Hussein had weapons of mass destruction - why else make life so difficult for the United Nations inspectors?)

It was easy to feel the inclusiveness of Sunday's march if you were part of it. It took 15 minutes to move a single block, and the reaction of most people to so much waiting around was to strike up conversations with whomever was around them. Some talked politics. Others joked about the signs they had made. But every one I saw was relaxed about speaking with strangers and hearing them out. Call it courtesy. Call it demonstration etiquette. In the end it amounted to a pervasive gentleness. The earnestness of the protest (its symbols ranged from fly swatters bearing the president's face to pallbearers carrying mock coffins draped with American flags) was its strong suit. Those in wheelchairs had an easy time getting around, and people went out of their way to make room for the many mothers with strollers.

The chant I heard most often was, "This is what democracy looks like!" And in the context of Sunday, the chant referred not only to the look of the crowd but to its belief that in an election as tight as this one, political self-restraint trumps political self-indulgence every time.

Nicolaus Mills, a professor of American studies at Sarah Lawrence College, is the author of "Their Last Battle: The Fight for the National World War II Memorial."

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