DAVIS, Calif. — In a rally here last week, 9,000 people came to hear Senator Bernie Sanders speak, some catching a glimpse from a parking garage roof.

In Palo Alto, Calif., some of his 4,000 fans there pitched tents and put up umbrellas for shade from the sweltering sun. The wait to get into his speech in Irvine, Calif., where 6,000 people packed into an amphitheater, stretched to five hours.

One of those waiting was Al Pappalardo, 59, a school psychologist who brought his daughter Alix, 22, along to what he called Mr. Sanders’s “last stand.”

“It is like a farewell tour,” Mr. Pappalardo said. “She’s going to think back and say: ‘I actually participated. I didn’t sit back.’”