California Sen. Kamala Harris undoubtedly will receive a warm reception from supporters Sunday when she opens her first California campaign office in her hometown of Oakland.

But the reception elsewhere in her native state is growing downright chilly, according to a new poll.

Harris is running a distant fourth in the Democratic presidential race in California, behind surging front-runner Sen. Elizabeth Warren of Massachusetts, former Vice President Joe Biden and Vermont independent Sen. Bernie Sanders, according to a Berkeley IGS Poll released this week.

She’s even running fourth among voters in the Bay Area. Harris grew up in Berkeley, went to law school in San Francisco and served two terms as San Francisco’s district attorney.

Harris has the support of 8% of likely Democratic voters surveyed. That’s down from 13% in the survey outfit’s June poll, and far less than the 29% supporting Warren in this poll. Biden is at 20% and Sanders is at 19%. Only 8% of the survey’s respondents are undecided.

Californians have elected Harris three times, twice as attorney general and once to the Senate. But Democratic voters are souring on her, the new poll indicates. The number of respondents with a favorable view of her has dropped 15 points since June, to 59%. Her unfavorable rating has increased to 25% from 15% three months ago.

The online survey was conducted in English and Spanish from Sept. 13-18 among 2,272 Californians likely to participate in the state’s March Democratic primary. The margin of error was estimated at plus or minus three percentage points.

Harris’ campaign aides remain upbeat.

“We have a strong operation in California that is only beginning to ramp up,” said state campaign spokeswoman Maya Humes.

“Kamala has already been endorsed by more than 150 California leaders, and thousands of Californians have participated in our campaign’s organizing trainings,” Humes said. “Kamala will continue to campaign hard here and talk to as many voters as possible about her agenda to tackle the issues that keep California families up at night.”

However, it is not just California that is tuning out Harris. A Des Moines Register/CNN/Mediacom Iowa Poll this week had her in fifth place in the first-voting state of Iowa, with 6% of the vote.

One small bit of consolation for Harris: She isn’t the least-popular California candidate among Californians, according to the Berkeley IGS Poll. That would be former San Francisco hedge fund manager Tom Steyer. Fewer than 1% of the voters surveyed support him.

Harris semi-famously said recently that she was “f—ing moving to Iowa” to concentrate on campaigning there. But this weekend, it’s the Bay Area.

On Sunday, Harris will officially open her new campaign headquarters at 3 p.m. at 3909 Grand Ave. in Oakland. She will also appear at a fundraiser Saturday at August Hall in San Francisco.

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