Support is falling for Gov. Jerry Brown’s proposal to raise income and sales taxes to balance the state budget, according to a new survey from the independent Public Policy Institute of California. Backing for a rival measure to raise income taxes and dedicate most of the money raised to the public schools is also eroding.

Brown’s measure, Proposition 30, would increase taxes on earnings over $250,000 for single people and $500,000 for couples and increase the sales tax by 1/4 cent on the dollar. Both tax hikes would expire after four years.

According to the poll, 48 percent of likely voters now support the measure while 44 percent oppose it and 8 percent are undecided. A month ago Proposition 30 led by a margin of 52 percent to 40 percent.

The measure drew strong support from Democrats but a majority of Republicans said they intended to vote no. Independents were about evenly divided.

While the money raised by Proposition 30 would go into the state’s general fund, Brown has said the revenue would help prevent cuts to school spending, and the current budget includes a provision that will trigger reductions in the schools’ funding if the measure fails.

Proposition 38, which would increase income taxes on all but the poorest Californians and set most of the money raised for the schools, was doing even worse in the poll.

The proposal was failing by a margin of 39 percent to 53 percent.

To see the full poll, go here.

Daniel Weintraub