More than 100,000 people demonstrated peacefully in Washington, D.C. to oppose a military strike against Iraq. Another 50,000 or more, depending on the estimate, marched in San Francisco. Simultaneous demonstrations unfolded across the country from Seattle to Raleigh, N.C., and in major cities around the world. It was, by general agreement, the largest day of anti-war protest since the Vietnam era.

A single weekend of protest, even at this level, is no sign of massive popular discontent with the president or of deep, widespread opposition to war with Iraq. But it would be misleading to suggest that these demonstrations were simply one more gathering of the anti-war clan. The size and tone of the protests hinted at a restlessness with President Bush's war policy — a sentiment often uncovered but not fully captured in public-opinion polls.

By all accounts, the protests included large numbers of Americans who don't typically express their political views in the street. Some said they'd never marched before; some showed up bearing such distinctly non-revolutionary messages as "Nebraskans for Peace." In contrast to recent anti-globalization protests in Washington, when militants wanted to "paralyze the city" and police arrested 600 people, this Washington march was peaceful from beginning to end, with only three arrests.

The numbers also were notable. Vietnam provoked no protest of comparable size until 1967, three years after the Gulf of Tonkin resolution gave President Lyndon Johnson authority to expand the war. By that time, the United States was deeply involved in Vietnam and Johnson was losing the public's confidence.

Protests in the year 2002 might convey a stronger sense of grass-roots energy to the average American if they departed more often from a well-worn path. When the speakers still include Ramsey Clark and Jesse Jackson, when the signs still include "No War for Oil!" even sympathetic observers may feel that the message and its expression are thoughtless leftovers from the last war.

This time, however, the rituals of anti-war protest coincide with a broader public unease. The demonstrations suggest, as the polls do, that the Bush administration would be unwise to assume a deep level of public support for its policies on Iraq.

The polls consistently have shown majority support for action to disarm or remove Saddam Hussein. As is well known, however, that support drops sharply when even modest conditions are attached: Do you support war even if the United States must act alone? Do you support a war with significant American casualties?

Election analysts have found — somewhat to their own surprise — that the Iraq issue is at best a mixed blessing for Republicans. Why? Because the people most likely to regard the war as a crucial issue are those who oppose it. Among those who consider Iraq the most important issue in the fall campaign, 66 percent oppose war and 33 percent favor it.

Some anti-war protests represent the opinion of an isolated few. Last weekend's demonstrations are not that easy to dismiss. Many Americans who might choose another form of expression are just as deeply troubled by the prospect of war.