Public support for Gov. Jerry Brown's ballot initiative to raise taxes has slipped to just more than 50 percent, a precarious majority with a growing number of voters now undecided, according to a new Field Poll.

Less than two months before Election Day, 51 percent of likely voters support the Nov. 6 initiative to raise the state sales tax and income taxes on California's highest earners, according to the poll.

That level of support, down three percentage points from July, is "ominously close to 50," poll director Mark DiCamillo said.

Meanwhile, the proportion of likely voters who are undecided grew five percentage points, to 13 percent.

The poll, co-sponsored by the Institute of Governmental Studies at University of California, Berkeley, is Field's first measure of Proposition 30 since the Howard Jarvis Taxpayers Association began airing radio ads against it. The spots highlight Brown's approval of initial construction of California's $68 billion high-speed rail project, as well as legislative pay raises and the recent state parks scandal.

The effect is unclear. While support for Proposition 30 has dipped marginally, the Democratic governor's own public approval rating ticked up slightly, to 47 percent.

Brown's measure continues to outpoll a competing measure backed by wealthy civil rights lawyer Molly Munger and the California State PTA. Support for Munger's tax initiative, Proposition 38, dropped five percentage points from July, to 41 percent, according to the poll.

Her effort could still frustrate Brown's, however. Though 35 percent of likely voters support both tax measures, 7 percent of likely voters support Proposition 38 and are opposed to or undecided about Proposition 30, according to the poll.

Though that group of exclusively pro-Munger voters is smaller than the 17 percent of likely voters who support Brown's initiative and oppose or are undecided about Proposition 38, it is not insignificant.

"Seven percent could contribute to a defeat if they don't get above 50 percent on Election Day," DiCamillo said.

Support for a third ballot measure, involving changes to the state's corporate tax formula, remained below 50 percent. Likely voters favor Proposition 39, backed by billionaire Tom Steyer, 45 percent to 39 percent, according to the poll.

The survey comes before either Brown or Munger begin to advertise significantly in the final weeks of the campaign. Brown has raised about $15 million for the effort, while Munger continues to self-fund her campaign, donating another $5 million on Monday.

Though the voter mood is improving, both initiatives will face an electorate skeptical of California's overall direction and not eager to pay higher taxes.

A majority of likely voters – 52 percent – say the state is seriously off on the wrong track, according to the poll. That's down from 64 percent in July.

Forty-eight percent of likely voters say they pay about the right amount in state taxes, while 40 percent say they pay more than they should. Just 9 percent of likely voters say they think they pay less in state taxes than they should.

Jack Citrin, director of the Institute of Governmental Studies at UC Berkeley, said the relatively high proportion of likely voters who think they pay about the right amount in state taxes is encouraging for Brown.

"If there were really a strong sentiment there saying 'I'm paying way too much in taxes now,' I think that would be a bad sign," Citrin said. "There doesn't seem to be that kind of really heavy resentment of the level of taxes being paid."

Brown has tried unsuccessfully since taking office to raise taxes and made Proposition 30 a priority of his administration this year.

He has tied the measure inextricably to school funding. The state budget he signed this summer requires about $5.4 billion in cuts to schools and community colleges if Proposition 30 fails.

Opinions about Brown's measure are highly partisan, with Democrats largely favoring the measure and Republicans opposed. Independent and other voters favor the initiative, 57 percent to 30 percent, according to the poll.

Zela Headlee, a retired homemaker who lives in Fresno, was among those contacted by Field. She said the middle class is overtaxed and, "I think we need a break."

But Headlee, a Democrat who is in her 90s, also worries about school funding. She said of the 74-year-old, third-term governor, "I like old Brown," and she may vote for his tax measure.

"I'm kind of up in the air about it," Headlee said. "I have grandchildren in schools."

Dustin Hernandez, a call center analyst who lives in Sacramento, said the state is too inefficient and wasteful to trust with more tax money.

"They haven't done a good job to begin with in managing the budget," the 31-year-old Republican said.

© Copyright The Sacramento Bee. All rights reserved.

• Read more articles by David Siders

Order Reprint