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.