Three out of four South Bay and San Francisco voters are willing to pay a higher sales tax to fund an expansion of Caltrain, a new poll found.

The poll, conducted for the Silicon Valley Leadership Group and this news organization, asked registered voters in Santa Clara, San Mateo and San Francisco counties if they would support a proposed sales tax increase of one-eighth of a cent to ease traffic, double the ridership capacity on Caltrain and complete the full electrification of the system. Seventy-six percent of the respondents said yes, compared to 18 percent who said no and another 6 percent who were undecided.

Burlingame resident Dennis Gale called the tax “desperately needed.” He moved to the Peninsula suburb from New York City eight years ago, choosing a condo within walking distance of a Caltrain station.

“It’s one of the first things we checked out,” Gale said. “When you live on the Upper West Side of Manhattan, you’re so used to having really convenient transportation. And, we chose an old suburb like Burlingame because it was more compact, there are more restaurants and stores close by, so it was almost like living on the Upper West Side.”

The results bolster an earlier poll conducted for the leadership group in May that found 74 percent of likely voters supported the tax proposal, which may appear on a ballot in 2020 and is expected to raise $80 million annually. It would need a collective two-thirds vote between the three counties to pass.

The leadership group has been polling this question for several years, said Carl Guardino, the group’s president and CEO. But the May poll was the first time support was strong enough to consider a ballot initiative, he said. And, with traffic seeming to grind ever slower on Highway 101, he was not surprised.

“Everyone’s favorite nightmare is Highway 101,” he said. “If we can grow (Caltrain service), that transforms not only Caltrain, that transforms the 101 parking lot. That’s why this is so critical.”

Caltrain’s $2 billion electrification project will replace 75 percent of its diesel train cars with electric ones, resulting in an estimated 30 percent increase in capacity and faster travel times, said Caltrain spokesman Seamus Murphy. When that project is completed sometime in 2022, Murphy said the agency will then set its sights on completing the electrification of its fleet, purchasing more train cars and increasing service frequency and doubling weekday ridership with the ultimate goal of transforming the commuter railroad into a fully-fledged mass transit system, similar to BART.

But, there’s one big problem, he said, and that’s funding. Unlike BART, which relies partly on dedicated property and sales taxes to operate the system and make capital improvements, Caltrain has no dedicated funding source, save for riders’ fares, rental income and parking or other fees. Instead, the transit districts in San Francisco, San Mateo and Santa Clara all contribute voluntary payments to Caltrain.

That system worked well for a while — contributions from the three transit agencies increased steadily between 2001 and 2010. But, when the recession hit, all those transit agencies cut their contributions, and they haven’t increased with the rising economy. The expected 2018 contribution is $20.5 million, 48 percent below the 2010 contribution of $39.4 million, even though ridership is now 56 percent higher than it was in 2010, peaking in 2016 at more than 19 million riders.

“This is not a formula for success,” said Jeannie Bruins, a Los Altos councilmember and chair of Caltrain’s governing board. “With all the traffic congestion in the Bay Area, we need to make forward progress on all forms of congestion management and transit solutions.”

Still, some residents say they feel all taxed out. Daly City resident Thomas Boyer does not typically ride Caltrain, and he said he likely won’t, so long as it only goes in one straight line up and down the Peninsula. Even though he’s not opposed to the idea of improving mass transit in general, he’s tired, he said, of all the taxes.

“I’m worn out with the frequency of these ballot initiatives,” he said. “I just am.”

About the poll: The poll of registered voters in San Mateo, Santa Clara and San Francisco counties was conducted by J. Moore Methods Inc. Public Opinion Research for Silicon Valley Leadership Group and the Bay Area News Group. Silicon Valley Leadership Group provided funding for the poll with significant financial support from Facebook. The poll, conducted from Dec. 27 to Jan. 9, has a margin of error of +/- 3.4 percent