Donald Trump flew the proverbial white flag over California last week by sweeping through the Bay Area and Central Valley for big-money fundraisers and then flying away without a making a single public appearance.

But his state political director and many of his most ardent Bay Area supporters say they are just beginning to fight, and to the befuddlement of political experts, they say that at least for now they will try to win over voters in bright blue California rather than swing states like Nevada.

Trump supporters insist that California is winnable because there are untold numbers of closeted devotees who won’t publicly support a candidate whom many Californians brand as a racist — an accusation that has also stuck to them.

“There is a narrative that we are all bigots and whackadoodles,” said Peter Kuo, a Santa Clara resident and former candidate for Congress who is serving as Trump’s Bay Area volunteer coordinator. “We’re not. We’re normal Americans who are supportive of Mr. Trump.”

Volunteers are nearly as central to Trump’s campaign strategy as free media coverage. With less money at his disposal than recent GOP presidential nominees — but a devoted core following — Trump needs to convert the passion displayed at his rallies into a volunteer force that will knock on doors and call undecided voters on his behalf.

But when it comes to establishing a ground game, Trump remains far behind Democrat Hillary Clinton, who already has Bay Area volunteers knocking on doors in Reno.

With the election now shifting into full gear, Trump’s local supporters are finally starting to pound the pavement, although they’re getting a decidedly mixed reception.

More than 100 people attended a volunteer training session at a Sunnyvale office park last week, and last weekend nearly 20 volunteers hung Trump banners on an Orinda overpass.

“We got a lot of honks and a few middle-finger salutes,” said Patty O’Day, a Trump supporter from Hercules. One driver tossed a fruit cup at them.

Stringing banners along a freeway overpass isn’t exactly what the Trump campaign had envisioned last spring when more than 100,000 Californians signed up to help support his primary run.

Kuo, a Taiwanese-American, said he’s gotten about 350 volunteers signed up from San Francisco to Santa Cruz counties. And volunteer sessions held in the Central Valley and Southern California have drawn big crowds, said Tim Clark, Trump’s California political director.

However, Clark declined to estimate how many volunteers have been trained statewide. The campaign also refused to allow reporters into last Tuesday’s volunteer training session in Sunnyvale — the first one it held in the Bay Area.

Clark said the campaign’s focus for now will be on winning California rather than helping rally support in swing states.

“We’re preparing to do anything we can to get our state into the mix,” he said. “When you have the number of volunteers that we have out here, anything can happen.”

The prospect of Trump volunteers knocking on doors and calling voters in the liberal Bay Area is “kind of ludicrous,” said Lanhee Chen, who served as policy director for Mitt Romney’s 2012 presidential campaign.

Romney directed his California volunteers to call swing states and knock on doors in Nevada, said Chen, now a research fellow at Stanford’s Hoover Institution. “Maybe they know something I don’t about Trump’s ability to be competitive in California, but it’s just a complete waste of resources.”

What makes Trump’s strategy more baffling is that while the latest Field Poll shows him trailing by 30 points in California, several other polls give him nearly even odds of becoming the first Republican to win Nevada since George W. Bush in 2004.

“Donald Trump is gaming and glitz, and that’s just Nevada,” said Eric Herzik, a professor of politics at the University of Nevada, Reno.

There’s little doubt an influx of GOP volunteers from California could boost Trump’s prospects in the Silver State, he said.

Four years ago, Herzik said, he saw several Democratic volunteers but no Republicans canvassing his section of Reno, even though he and many of his neighbors are registered Republicans.

“Knocking on doors is still a very effective way to get out the vote,” he said, “and the Republicans could use all the help they can get here.”

Clinton volunteers in San Francisco have already organized a volunteer bus to Reno leaving every weekend. An Alameda County volunteer group is setting up its own weekly bus trip, said Vincent Leung, who heads the Alameda County for Hillary campaign team.

Last weekend, the group trained more than 50 volunteers in Hayward how to respond to voter questions about her emails, the Clinton Foundation and everything from Whitewater to the Second Amendment.

“We want everyone staying positive and on message,” Billy Cline, Clinton’s Northern California organizer told the group assembled at the Carpenters Local 713 union hall. “Your objective is to have a conversation. Let them relate to you.”

Trump supporters say they find lots of secret compatriots, but that it’s hard to relate to voters who think they’re supporting a racist.

“If I say Trump, their eyes go red,” said Larry Grogan, a San Leandro resident who attended a Trump volunteer session last Sunday sponsored by the Alameda County Republican Party.

O’Day, who also attended the event, said her car has been keyed so many times because of her GOP-themed bumper stickers that she now has Trump bumper magnets that she takes off her car after she parks. “Our people are afraid to go out,” she said, “and we have to make them not afraid.”

David Erlich, the chairman of the Alameda County GOP, joked that the 15 prospective volunteers — nearly half of whom were black or Latino — looked so traumatized that they “sounded like an AA group.”

Those Trump supporters attending the training in Sunnyvale were mostly white.

Trump volunteer Sammy Castillo, who is Native American, isn’t letting the California polls get him down.

He said the only polls he cares about are informal ones he conducts in his heavily Latino East San Jose neighborhood. Even though he’s gotten grief about his Trump sign, he said about half of the people he’s spoken to tell him they’re secretly planning to vote for Trump.

“He may not win California, but I think it’s going to be a really close race,” Castillo said as he handed out Trump stickers outside the Sunnyvale meeting. “I feel it coming. And I’ve never been wrong yet.”

Contact Matthew Artz at 510-208-6435. Follow him at Twitter.com/Matthew_Artz.