LOS ANGELES (AP) — Public support appears to have slipped for a California ballot proposal that would require doctors to submit to random drug tests, signaling a volatile campaign that could become the most costly race in the state this year.

With two months to go before the election, physicians, medical groups, insurance companies and other opponents trying to derail Proposition 46 have already contributed over $50 million to the effort.

The contest is being depicted alternately as either an attempt to enhance patient safety or a potential windfall for trial lawyers. If approved, the wide-ranging proposal would lift the ceiling on damages for pain and suffering caused by medical negligence for the first time in decades, to $1.1 million from $250,000. Another provision would require doctors to check a statewide database before prescribing powerful drugs, such as painkillers, in an attempt to reduce abuses.

A key finding of an independent Field Poll released Thursday was that nearly 1 in 3 voters remains undecided on the three-pronged proposal, up sharply from a Field survey about two months ago.

"Voters are finally starting to understand that there is an election coming up in two months, and they haven't been paying attention," pollster Mark DiCamillo said.

The poll found that about 1 in 3 likely voters support Proposition 46, or 34 percent, a 24 percentage point slide from the earlier Field survey. However, DiCamillo said differences in the wording of questions posed in the two polls could account for some of the sharp shift, along with other factors.

Jamie Court, the president of Consumer Watchdog, an advocacy group backing the proposal, said the poll showed the race was in flux.

"The whole game is to get their attention," Court said. "If they haven't made up their minds … the whole field is wide open."

The attempt to impose drug and alcohol testing, which would apply to doctors with hospital privileges, is being watched closely outside the state, and the campaign has attracted a long list of influential political players, including Democratic Sen. Barbara Boxer, who says in an ad that the proposition will "make sure impaired doctors don't treat someone you love."

Jason Kinney, spokesman for the committee opposing the proposal, said support was expected to quickly drop once "voters started taking a long, hard look at the risks and the costly details."

The poll also found a separate measure to allow the state insurance commissioner to review rate changes, Proposition 45, has the support of 41 percent of likely voters. The survey found 26 percent are opposed and 33 percent are undecided.

The Field Poll interviewed 467 likely voters from Aug. 14-28. It has a sampling error margin of plus or minus 4.8 percentage points.