DENVER — Despite the prospect of the nomination of Senator Obama, a self-proclaimed candidate of change who made a name for himself by speaking out against the war in Iraq, the anti-war movement is gearing up for a big convention week here.

This year’s convention marks the 40th anniversary of the Democratic National Convention in Chicago, where anti-war protesters battled with police and disrupted the nomination of Hubert Humphrey. Although it is unlikely that anything approaching that scale will happen at the Denver convention, many demonstrators are organizing — optimistically, perhaps — under the banner of the Recreate 68 Alliance.

As a political matter, the circumstances surrounding this year’s nomination of Mr. Obama, in part on the basis of his opposition to the Iraq war, are vastly different from that of Humphrey in 1968. Humphrey had, after all, served in the administration of President Johnson, who inherited the Vietnam War from President Kennedy and then intensified it. The protests this year are more likely to be on the scale of the 2000 Democratic National Convention in Los Angeles, where a fracas erupted between protesters in the designated protest zone and police, or the 2004 Republican National Convention in New York, where hundreds were arrested.

Protest groups have ambitious plans for this week, including major appearances by two anti-war presidential candidates: the Green Party’s nominee, former congresswoman Cynthia McKinney, and a former Green Party candidate nominated at the party’s 2000 convention in Denver who now is running as an independent, Ralph Nader.

On Saturday, talk of protest filled a public transit bus heading into the city from Denver International Airport. One woman wore a bright orange shirt decrying a possible attack on Iran, while other passengers traded protest tips and suggestions.

The festivities kicked off in earnest with a series of marches yesterday. Protesters trooped up and down the 16th Street pedestrian mall and around downtown landmarks, chanting: “If you support the troops, bring them home,” “This should be a peace convention,” and “We support war resisters.” Members from a group called Iraq Veterans Against the War, dressed in desert fatigues and black shirts, shook their fists and shouted, “Bring our brothers home.” And better-known groups such as United for Peace and Justice and Code Pink were in evidence.

More menacingly, at points during the day a group of masked bicyclists rode in unison throughout the city. Other protesters kept their faces hidden behind kerchiefs and brandished wooden sticks with orange or black flags, associated with the anarchist movement. These protesters declined to identify themselves when asked about their appearance, agenda, or cause. (Orange has become a popular color among the anti-war set, as it symbolizes the clothing of the detainees at Guantanamo Bay, Cuba.) Still, unlike the anti-globalization protests in Seattle in 1999, where Starbucks coffeeshops were a prime target of anarchists, demonstrators left the more than five outlets of the chain on a one-mile stretch of 16th Street untouched.

The presence of the protesters caught the eye of a prominent member of the 1960s anti-war movement and former California state legislator, Thomas Hayden, who is backing the presidential effort of Mr. Obama and is involved with the group Progressives for Obama. “You can’t re-create ’68 because this isn’t ’68,” Mr. Hayden said. Of the protests, he added, “It’s not very large. It won’t affect the outcome of the general election.”

Still, organizers said it is important to challenge the Democratic Party. “Is he anti-war? I’m seeing a lot of slipping,” a founder of Code Pink, Gael Murphy, said of Mr. Obama.

She criticized the Democrats for being too pragmatic in their political decision-making. “Good policy is good politics. Why the Rahm Emanuels, the Nancy Pelosis, the Steny Hoyers, and the Deans don’t understand that is beyond me … ,” she said. “We’re here to remind the Democrats that they don’t get a free ride.”

The national coordinator of United for Peace and Justice, Leslie Cagan, turned Mr. Obama’s slogan against him. “Change I can believe in is change I can see,” she said. “We want Barack Obama to know that if he’s elected, we’re going to keep pressuring him.”

While yesterday’s big issue was the ongoing war in Iraq, the protesters’ ire is expected to shift later in the week to the prospect of military conflict with Iran. Tomorrow night, a group called World Can’t Wait is hosting a showing of a documentary, “Iran is Not the Problem.”

Code Pink’s Ms. Murphy said she not only opposed a military strike on Iran but even tough economic sanctions on the regime, which the Bush administration has said is developing nuclear weapons. “Don’t go to war with Iran. … What laws have they broken?” she said. “We are trying to make trouble in the Middle East. … You’re going to turn the people against us.”

Denver police, some in riot gear, were a major presence throughout the city. As of yesterday evening, their interactions with demonstrators, some of whom were blocking intersections, were peaceful. There will be four more days for things to heat up.

gitell@aol.com