Next time you're riding Muni and a stranger taps you on the shoulder, be polite. She could be your next mayor.

You'll know it's her by the fiery red hair, the sky-high Chanel heels and the campaign literature she thrusts in your hand. She won't be dissuaded by earbuds and will ask you to take them out. She won't leave you alone if you tell her you don't live in San Francisco, don't follow politics or don't vote.

"Hi, I'm Joanna Rees," she'll say. "And I'm running for mayor."

The crowded, lurching 38-Geary may not be the likeliest place for the 49-year-old former venture capitalist who lives in Presidio Terrace to be seen. But she rides a Muni bus three mornings a week to talk to people about their concerns.

"We're a great city, and we're not living up to our greatness," she said. "When I'm out in the community, I almost feel like I'm on an apology tour. I'm so sorry the streets are so dirty. I'm so sorry Muni was late. I'm so sorry your kid didn't get into the school you wanted."

Often, the riders are surprisingly receptive. Sometimes they're not.

"I know you're trying, but I don't know you," said Marian Hayama, a 73-year-old sitting in the front row. "I have to go with someone I know."

Across the aisle, John Harris, an 83-year-old in a natty pinstriped suit was more impressed. "Don't let nobody stop you, baby, do it!"

Rees doesn't plan to let anybody stop her on her way to City Hall. She shuttered the offices of her venture capital firm in May and is running for mayor 17 hours a day, seven days a week.

She says she has knocked on 9,000 doors, talked to 650 merchants and chatted up thousands of Muni riders on 30 bus lines. She has raised more than $360,000 in private contributions and $470,000 in public financing, placing her among the top earners in the race.

Despite all this, Rees is barely registering a blip in polls. But don't bother telling her that - she has no backup plan.

"People are 100 percent undecided," she said. "I can't tell you how many doors I knock on and they think Gavin Newsom's still mayor."

And don't bother telling her interim Mayor Ed Lee, who announced he was running for a four-year term just weeks ago, has damaged her chances even more.

"I was running against eight insiders, then it was nine and now it's 10," she said.

If you really want to get Rees riled up, bring up the oft-mentioned notion that she's the Meg Whitman of the San Francisco mayor's race. Whitman was the former eBay CEO who ran for governor with no political experience and a spotty voting record. Rees, too, has never run for office and after registering to vote as decline-to-state in San Francisco in 1992, skipped about two-thirds of elections.

"I'm not a Meg Whitman - in no way," Rees said flatly, saying she's more liberal, doesn't wall herself off from the media or voters, and became successful despite a childhood of powdered milk and thrift stores.

The second of four children, Rees was raised in New Jersey by a stay-at-home mother, a former schoolteacher, and a father who started one failed business after another. She graduated from Duke University and put herself through business school at Columbia University.

Her first husband abandoned her and their baby boy shortly after she graduated, leaving her saddled with debt. She and her second husband, who had a daughter, moved to San Francisco, where she worked in finance.

In 1996, Rees created Venture Strategy Group, later called VSP Capital. She lived on her savings for three years, but eventually became one of the few women to make it big in venture capital.

She's married for the third time to her former VSP partner, John Hamm, now the CEO of a software startup in Santa Clara. Rees' son, Arthur, is in business school at Santa Clara University, and her daughter, Taylor, just started college in Boulder, Colo.

Whatever happens on election day, Rees said she's entering the public service era of her life. If that's as mayor, she'll start by making all department heads - including former City Administrator Lee - resign and reapply for their jobs. She'll also demand that they start from scratch in their budgets, explaining why each dollar is needed.

She sent her children to pricey private schools, but said she'll focus on improving the public schools by encouraging philanthropists to help fund them and pushing the school district to adopt an entirely neighborhood-based assignment system.

She'll also fight to scrap the city's payroll tax and recruit more foreign businesses.

It was this focus on jobs that excited Tim Tonella, a 47-year-old head of an executive search company. When he answered a knock on his Inner Sunset door several weeks ago, he was surprised to find Rees.

"I had never had anyone come to my door who was running for a major public office," he said. After talking for a half hour, Tonella was sold. He's voting for Rees, donating to her campaign and planning to host an event to introduce her to colleagues.

For Rees, it was one more San Franciscan down. Thousands more to go.