SAN FRANCISCO — The Silicon Valley venture capitalist Keith Rabois, onstage in January at a tech conference, said his first choice for president was a Democrat, Pete Buttigieg.

And, sure, it would be a close call for Joseph R. Biden Jr. over President Trump. But Bernie Sanders?

At that, Mr. Rabois, who has been a top executive at or invested in LinkedIn, Square, Yelp and PayPal, balked. Speaking to the crowd, he drew the line at democratic socialism. (Mr. Buttigieg ended his campaign on Sunday night.)

“I would certainly vote for Trump over Sanders,” Mr. Rabois declared.

When it comes to the 2020 Democratic primaries, with California poised to allocate hundreds of delegates this week on Super Tuesday, many tech leaders in Silicon Valley have a plea: Anyone but Sanders.