Oakland police fire tear gas as they prepare to move in to Frank Ogawa Plaza to disperse Occupy Oakland protesters on Tuesday. (JANE TYSKA/AP)

As police start ousting protesters, a disparate movement — one that has been embraced by many Democratic politicians and labor organizations — is struggling to respond.

Protesters in other cities are worried about suddenly finding themselves in a clash with police. And even if the vast majority of protesters are peaceful, violent provocateurs could tarnish the movement’s image in the eyes of the public.

Just as Democrats tried to tie Republicans to the most extreme tea party activists, the Massachusetts Republican Party is already attacking Democratic Senate candidate Elizabeth Warren as the “Matriarch of Mayhem” for saying she helped create an intellectual foundation for the protests.

Pollster Stan Greenberg argues that the violent clash in Oakland won’t much change public opinion, pointing out that there was already a large gap between support for the goals of the movement and support for the movement itself, suggesting there’s already “some ambivalence on methods” — an ambivalence that has always existed about civil disobediance, including during the civil-rights movement.

“My guess is that people are not surprised by these moments. I think it’s factored in” to pre-Oakland public opinion, Greenberg said.

Most Occupy gatherings have been peaceful, and protesters have developed good working relationships with the police. Most disputes have been over logistical issues like garbage and drumming.

That peace was disrupted Tuesday night in Oakland, when the city sent riot police to clear protesters out of a public park, saying they could no longer camp there.

The police fired tear gas and bean-bag shots (and possibly rubber bullets and flash grenades) at protesters to to prevent them from regrouping. Occupiers responded with paint, bottles and rocks. A fence was erected around the area; protesters tore down the fence and re-occupied.

Other Occupy groups have been disbanded by police. In Atlanta, the mayor ordered the protesters removed in the middle of the night. About 50 were arrested and went peacefully, avoiding a confrontation. But now they have no place to camp.

AFL-CIO President Richard Trumka stood firmly on the side of the Occupiers, saying that labor leaders “are extremely alarmed by the increasing number of arrests of peaceful protesters across the country and call on elected leaders to stop ordering the police to make these arrests.”

Rep. Barbara Lee (D-Calif.) echoed Trumka, expressing “outrage and grave concern about the policy brutality.”

Labor groups in Baltimore — including the police and firefighters’ unions — wrote to the mayor asking him to let the protesters stay.

But not every Democrat wants to wade into a fight with the police. “I don’t think” the protesters have the right to ‘Occupy’ forever,” said Sen. Dianne Feinstein (D-Calif.) Wednesday. I don’t think people, for example, can sleep in a square for weeks on end. You have to have some order to it.”

And public pressure has prevented — or at least forestalled — police action in San Francisco, where a planned raid was called off on Thursday night. Protesters have rallied around an Iraq war veteran seriously injured in Oakland, inspiring anger at the police crackdown.

There has been some anger over the police response — in Oakland, thousands marched through the city after the camp was broken up. Occupy Atlanta says that support has been growing since the arrests.

Still, future clashes seem inevitable. In New York Wednesday night, protesters marched to Times Square in solidarity. Some broke through a police barricade; about a dozen were arrested. As Occupiers start to wear out their welcome with public officials, they will have to find a way to keep the movement going peacefully.

And Democrats will have to navigate dicey territory.

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