Several hundred protesters opposing Donald Trump have gathered outside the hotel where he was scheduled to speak to California Republicans.
A large contingent of police sought to head off violence like what followed a rally in southern California the night before.
A man wearing a Trump campaign “Make America Great Again” red hat was struck while being jostled by a group of shouting protesters.
“It went gangbusters. They attacked me,” said Chris Conway, who identified himself as a mortgage broker from San Mateo.
A dozen protesters linked arms to block the road in front of the hotel near San Francisco International Airport, but no one was using the street because police had already closed it to traffic. Protesters also draped a large “Stop Hate” banner outside the hotel.
In southern California, violent demonstrations led to 17 arrests as the Republican presidential contender brought his campaign to conservative Orange County on Thursday.
While Mr Trump held a rally at a fairgrounds amphitheatre, dozens waved anti-Trump signs outside in mostly peaceful protests and traded insults with masses of the candidate’s supporters who had lined up to see him. Later in the evening, however, the protests swelled and grew rowdy and spilled into the streets.
One Trump supporter had his face bloodied in a scuffle as he tried to drive out of the arena.
One man jumped on a police car, leaving its front and rear windows smashed and the top dented and other protesters sprayed graffiti on a police car and the Pacific Amphitheatre’s marquee.
Dozens of cars – including those of Trump supporters trying to leave – were stuck in the street as several hundred demonstrators blocked the road, waved Mexican flags and posed for selfies. Some protesters badgered Trump’s fans as they walked to their cars in the parking lot.
Police in riot gear and on horseback pushed the crowd back and away from the venue. There were no major injuries and police did not use any force. The crowd began dispersing about three hours after the speech ended.
Seventeen people were arrested, police said.