Clinton’s lead among California voters is slipping

Democratic presidential candidate Hillary Clinton holds a 12 point lead in the latest poll of California voters.

Democratic presidential candidate Hillary Clinton holds a 12 point lead in the latest poll of California voters. Photo: Joe Raedle / Getty Images Photo: Joe Raedle / Getty Images Image 1 of / 3 Caption Close Clinton’s lead among California voters is slipping 1 / 3 Back to Gallery

Presidential hopeful Hillary Rodham Clinton holds a comfortable 12-point lead over her closest Democratic rival in California, according to a Field Poll released Wednesday, though her lead in the delegate-rich Golden State, like across the nation, is slipping.

Forty-seven percent of likely Democratic primary voters recently polled in California support Clinton, down from 66 percent in May and 73 percent in February, the latest survey by Field Research of San Francisco shows.

Meanwhile, Vermont Sen. Bernie Sanders has seen his support surge from 9 percent to 35 percent over the same period, according to the poll.

When a Joe Biden candidacy is factored into the race — a possibility yet to be confirmed by the vice president — Sanders edges to within nine points of Clinton. Biden polls at a distant third, with 15 percent support. No other candidates have more than 1 percent support, and 14 percent remain undecided.

“Bernie Sanders has been making significant inroads across the country, and it’s reflected here in California,” said Mark DiCamillo, director of the Field Poll.

Sanders’ stronghold is with voters who are younger, more liberal and white, the poll suggests. Accordingly, his backing is greatest in the Bay Area, where he enjoys 38 percent support to Clinton’s 45 percent, as compared with the Central Valley, where he is supported by just 24 percent of Democrats, and Southern California, where he is supported by 34 percent.

Clinton remains strong with women, Hispanics and more moderate Democrats, according to the poll.

Her slide in the polls, not just in California but nationally, comes amid questions about her trustworthiness as well as her use of a personal e-mail server to conduct government business.

“Most of the news that is centered around Hillary has been about the e-mails,” said DiCamillo.

“That continues to be the 800-pound gorilla in the room.”

Still, Clinton enjoys nearly 42 percent support nationwide compared with Sanders’ 25 percent, according to an average of polls taken by the nonpartisan data aggregator Real Clear Politics.

While Biden remains in third place both nationally and in California, the Field Poll suggests that residents of the Golden State want him to enter the race, with 63 percent saying it would be a “good thing” for him to run.

“I think there may be a little concern that most of the attention, at least when it comes to debates, has been on the Republican side,” said DiCamillo, noting that a Biden candidacy would add more interest to the Democratic primary.

Many expect Biden to make a decision before Tuesday’s Democratic debate in Las Vegas.

Wednesday’s Field Poll surveyed 1,002 registered voters between Sept. 17 and Oct. 4, and reports a maximum sampling error of 0.5 percentage point.

Kurtis Alexander is a San Francisco Chronicle staff writer. E-mail: kalexander@sfchronicle.com Twitter: @kurtisalexander