After imploring Portlanders and out-of-town troublemakers this morning to refrain from violence at a planned Aug. 17 protest, Mayor Ted Wheeler was scheduled to appear tonight in San Francisco as part of a panel on homelessness.

But Politico reports that Wheeler, who is running for re-election next year, joined Oakland Mayor Libby Schaaf and San Francisco Mayor London Breed, who all pulled out of a "Solving Homelessness" panel at San Francisco's Commonwealth Club sponsored by Kaiser.

The move came as Kaiser workers in California prepare to walk out.

"Union officials confirmed Monday that Kaiser Permanente employees in California overwhelmingly authorized a strike in October, following a two-week voting period. More than 37,000 union members, or 98 percent, voted in favor of striking, according to SEIU-United Healthcare Workers West," Politico reported.

"Union leaders explicitly asked the mayors to withdraw and they agreed, SEIU-UHW spokesman Sean Wherley told POLITICO, arguing that it was important that elected officials recognize 'the role Kaiser plays in perpetuating income inequality in the Bay Area and across California.'"

Kaiser workers in Oregon and Southwest Washington also voted last week on whether to strike this year. The results of that vote have not yet been released.

Wheeler's spokesman, Tim Becker, confirmed the mayor will miss the San Francisco event.

"The mayor has a firm policy to never cross picket lines," Becker says in an email. "That, coupled with the urgency of the planned protests both played into his decision to cancel the trip to San Francisco."