Donald Trump is calling for Republican unity in the face of intense backlash.

In San Francisco, hundreds of protesters demonstrated outside the venue where Trump was about to speak to the California GOP convention. The crowds forced him to leave his motorcade and even scale a small barricade to get in through the back.

Many of the protesters were angry over Trump's stance on immigration. Once inside, the GOP presidential front-runner told the convention his entrance was "like crossing the border."

CBS News' Craig Boswell reports that with Trump less than 300 delegates away from clinching the GOP nomination, tensions are running high both inside and outside of the party. Establishment Republicans are accepting he could be their candidate, but opposition to the man and the message shows little sign of letting up.

"That was not the easiest entrance I've ever made," Trump said at the convention after protesters forced him to arrive on foot Friday. "Oh boy, felt like I was crossing the border actually. It's true. I was crossing the border, but I got here."

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Trump was in California ahead of the state's June 7 primary, where the most delegates of the nominating cycle will be awarded.

"I speak to the people in this room because there has to be unity in our party," Trump said. "There has to be unity in our party."

He's wooing mainstream Republican audiences who are showing signs of accepting he is the likely nominee.

"I will do my duty and vote for the man if it's Trump because I want a Republican in the White House," said Lois Shade of Glendora, California.

Trump now has 80 percent of the 1,237 delegates needed to clinch the nomination.

"I'm up by 400 or so delegates," Trump said. "I'll be up by more than 500 when it's over, and we'll be up by five million votes, OK?"

Ted Cruz addresses the same California audience Saturday. The Texas senator has been camped out in the crucial state of Indiana, which holds its primary Tuesday.

There, he picked up a key endorsement from the state's Gov. Mike Pence, who avoided taking shots at Trump.

"I'm not against anybody, but I will be voting for Ted Cruz in the upcoming Republican primary," Pence said on the Garrison radio show.

In an interview with CBS' "Face the Nation" airing Sunday, Cruz again responded to former House Speaker John Boehner, who referred to him as "Lucifer in the flesh," suggesting Boehner may want to return to Washington.

"I kind of wondered if Boehner was auditioning to be Donald Trump's vice president," Cruz said. "You know, a Trump-Boehner ticket would really say the Washington cartel in all its force - one has been funding the cartel, the other has been giving in to Democrats for years."

After Cruz addresses the California convention Saturday, it's back to Indiana, where the state's 57 delegates are seen as critical as to whether Cruz can stop Trump from winning the nomination before the GOP convention in July.