Even in blue California, Clinton’s numbers are slipping

Republican presidential candidate Donald Trump arrives at a rally at the Germain Arena in Estero, Fla. That state is looking more favorable for him than California, where he trails Hillary Clinton by a margin of 50 percent to 33 percent. less Republican presidential candidate Donald Trump arrives at a rally at the Germain Arena in Estero, Fla. That state is looking more favorable for him than California, where he trails Hillary Clinton by a margin ... more Photo: Joe Raedle, Getty Images Photo: Joe Raedle, Getty Images Image 1 of / 3 Caption Close Even in blue California, Clinton’s numbers are slipping 1 / 3 Back to Gallery

Even in politically deep-blue California, an increasing number of voters have an unfavorable impression of Democratic presidential nominee Hillary Clinton.

Clinton still holds a 17-point lead over Republican nominee Donald Trump in California, according to a Field/IGS Poll of likely voters released Tuesday — but that’s down from a 24-point advantage in July.

There’s still little chance of Clinton losing a state that hasn’t backed a Republican presidential nominee since 1988. But the new poll is a concern for her campaign all the same, because it’s evidence that her recent slippage in the polls is so broad-based that it extends even to her strongholds — and a state where she has raised millions of dollars at fundraisers.

A majority of those surveyed now view Clinton unfavorably, and what the pollsters called “a very large proportion of the state’s electorate” — 41 percent — have a very unfavorable opinion of her.

“She’s totally lost whatever benefit (in the polls) she had from the convention,” said Field Poll director Mark DiCamillo. “Much of the media’s focus over the past three weeks has been on Clinton, and you can see that she has not held up well in the national polls. And now you’re seeing the same thing in California.”

The pollsters were taking their survey during an especially bad stretch for Clinton, Sept. 7 through Sept. 13. Toward the end of that period, Clinton said half of Trump’s followers could be put in “the basket of deplorables” — racists, sexists, homophobes and xenophobes. Then she nearly collapsed after a Sept. 11 memorial service, and her campaign revealed afterward that she had been diagnosed with pneumonia.

A few days before the pollsters were in the field, the FBI released an 11-page summary of its interview of Clinton as part of its investigation into her use of a private email service for government documents. The bureau also revealed a 47-page overview of how it came to its conclusion that Clinton and her State Department staff had been “extremely careless,” though not criminally negligent, in their handling of classified information.

“The drumbeat of the email stuff goes on,” said Jack Citrin, director of the Institute of Governmental Studies at UC Berkeley, which conducted the survey with Field and YouGov of 1,426 likely voters.

The survey results reflect how Clinton “has this image of being slippery, unforthcoming,” Citrin said.

What’s not so clear, he said, is how much Trump has improved his standing among voters. Not only does Trump trail Clinton in the latest poll — she has 50 percent to his 33 percent — but 69 percent of the survey’s voters hold at least an unfavorable view of the GOP nominee and 56 percent of them have a very unfavorable opinion of him. Clinton leads Trump across all demographic categories except voters over 65 years old, those with a high school education or less, and born-again Christians.

Another sign of Clinton’s vulnerability is the level of support for Jill Stein. The Green Party nominee, who pulled 0.6 percent of the state vote in 2012, is at 6 percent in the new survey. Libertarian nominee Gary Johnson, who won 1.1 percent four years ago, is at 5 percent — though that’s half of what he was pulling in July.

Support for Stein and Johnson is strongest among voters ages 30 to 39 — part of the Millennial demographic that preferred Clinton’s opponent during the Democratic primaries, Vermont Sen. Bernie Sanders.

Both Stein and Johnson each score 13 percent among those who state no party preference, compared with 38 percent for Clinton and 24 percent for Trump.

Citrin said Stein and Johnson “are pulling a decent number” in California, with Stein in particular drawing more supporters from Clinton.

“The strength of those third-party candidates represents a dissatisfaction in the major-party candidates,” Citrin said.

Their challenge will be holding on to their momentum through the next seven weeks. Last week, the Commission on Presidential Debates did not invite Stein or Johnson to the first presidential debate, Monday at Hofstra University in New York, because they were not polling at 15 percent or better.

As the Nov. 8 election nears, Citrin said, Stein and Johnson will have to contend with the tendency of voters to avoid third-party candidates “if they don’t think their vote matters.”

Clinton acknowledged her challenges in reaching Millennial voters Monday during a speech at Temple University in Philadelphia, saying, “Even if you’re totally opposed to Donald Trump, you may still have some questions about me. I get that. And I want to do my best to answer those questions.”

The survey did include good news for Clinton: President Obama has a 58 percent approval rating among California voters, and that reflected glow will shine on Clinton for as long as Obama continues campaigning for her.

“Obama’s popularity will help Clinton,” Citrin said. “The more he’s out there, the better it is for her.”

The Field/IGS Poll did not supply a margin of error. Opt-in polls such as the online survey do not lend themselves to the calculation of sampling error as easily as traditional telephone surveys, DiCamillo said.

Joe Garofoli is the San Francisco Chronicle’s senior political writer. Email: jgarofoli@sfchronicle.com Twitter: @joegarofoli