The Coachella Valley is becoming a political battleground for a controversial health care ballot initiative that would raise the cap on medical malpractice damages and require drug and alcohol testing of doctors.

Supporters of Proposition 46 include U.S. Sen. Barbara Boxer, a prominent Rancho Mirage Democrat.

They say the measure would improve patient safety and fairly compensate people who have experienced negligent or improper treatment, raising potential damages from the $250,000 limit that was set in 1975 to more than $1 million.

But those who oppose the idea are hoping to explain to Coachella Valley voters that Prop 46 would significantly raise health care costs and disproportionately affect middle-income and older voters.

Filings with the Federal Communications Commission show opponents have already purchased more than $82,000 worth of local air time for television spots that run until the Nov. 4 election.

“We are running ads in the Coachella Valley because that’s an important (voting) bloc; in any election that’s a critical bloc of voters,” said Jason Kinney, a spokesman for No on 46.

“In a lot of ways, it’s a bellwether area.”

Health care has long proven to be an important election topic for Coachella Valley, a retirement hub that is home to about 170,000 people over the age of 65, according to data from the Health Assessment Resource Center.

Supporters of Prop 46 argue steps would be taken to discipline any doctor suspected of being impaired on the job, and require providers to consult a state prescription drug history database before prescribing certain substances.

“Prop 46 will save lives with drug and alcohol testing to make sure impaired doctors don’t treat someone you love, safeguards against prescription drug abuse and holds the medical industry accountable for mistakes,” Boxer said in the advertising campaigns.

Kinney said the initiative was written almost exclusively by trial attorneys and political consultants and that, despite a guise of patient-safety efforts and drug testing, the purpose is to increase the number of lawsuits and malpractice payouts for attorneys.

The state Legislative Analyst’s Office’s fiscal impact statement states Prop 46 — and the increased malpractice damages — would increase state and local government health care costs, “likely ranging” from tens of millions to several hundred million dollars annually.

But the analysis said “uncertain, but potentially significant” savings from new requirements like prescription drug monitoring or alcohol and drug testing could offset the costs.

Statewide, a Field Poll released last week found that voter support for the health-related ballot initiative had weakened, with 37 percent of likely voters leaning toward a “no” vote and 34 percent supporting it.

Another 29 percent were undecided.

Prop 46 had held a “comfortable lead” and much greater support earlier this summer, with 58 percent of those polled in late June and early July were likely to vote yes, the Field Poll noted.

And though the issues are medical, likely voters are tending to fall along strong, “significant” party lines, the Field Poll showed.

The majority of Democrats back the initiative, but 45 percent of Republicans opposed the bill. Younger voters also supported the measure more.

In the “other Southern California” category — which includes Riverside County — 33 percent of voters supported raising the liability cap and increasing substance abuse testing regulations. But the majority, 45 percent, would vote no.

Carmen Balber with Consumer Watchdog, which has supported the measure, is passionate about the potential of Prop 46.

She said that 103,000 health care providers have had a problem with substance abuse, and the Medical Board of California estimates that 18 percent of doctors will in their lifetime.

“This is a serious issue and one that is going completely unaddressed because no one has authority and frankly the interest in catching substance abusing physicians,” she said. “Doctors hold our lives in their hands; they should be held to the same safety standards as any other position.”