DONALD Trump has made his case to California's Republican establishment as protesters shadowed him from the southern to northern ends of the state and clashed with police.
Demonstrators swarmed outside the hotel near San Francisco airport where Mr Trump was scheduled to meet with local power brokers before giving a lunchtime speech at the state party's convention. On Thursday night, protesters tangled with authorities and damaged police cars after a Trump rally in Orange County.
Tensions mounted as the contest moves into its final stages in one of the nation's most liberal and diverse states. The state party convention amounts to the starting bell in the contest, with Ohio governor John Kasich appearing later on Friday and Texas senator Ted Cruz and his new running mate, Carly Fiorina, up on Saturday.
California's primary usually comes after the party nominees are known but this time looms as a decisive contest that could either clinch the prize for Mr Trump or force him into a contested convention in July.
All three candidates are looking to galvanise supporters, sway undecided party members or poach from rival campaigns at the convention. "It's going to be a free-for-all," predicted the state party vice chairman, Harmeet Dhillon.
That label clearly applied to Trump's Orange County rally on Thursday night, which filled the Pacific Amphitheatre to its capacity of about 8,000, with many hundreds more turned away.
Protests that stayed mostly peaceful during the event grew in size and anger afterward.
Police in riot gear and on horseback pushed the crowd back and away from the arena, and one Trump supporter had his face bloodied in a scuffle as he tried to drive away.
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 venue's marquee.
About 20 people were arrested, said the Orange County Sheriff's Department.
On Friday, hundreds of demonstrators pushed to the front doors of the Hyatt Regency in Burlingame before being moved back by police in riot gear. Some protesters infiltrated the hotel building and hung a giant banner reading, "Stop Hate." State party chairman Jim Brulte said demonstrators had tried to block Mr Trump's motorcade but that the candidate got through.
Mr Trump's remaining rivals cannot beat him in what is left of the primary season. Their only hope is to deny him a majority of delegates heading into the July convention and wrestle for the prize in multiple ballots there.
But questions persist in the party - nationally and in California - about Mr Trump's electability and his conservative credentials. So the reception Mr Trump in particular receives from the state's party activists and grassroots organisers will be noteworthy.