What do you get when you pit doctors against trial lawyers in a high-stakes political death match in the most expensive state in America? A race that’s likely to be the most expensive contest of the year.

The two big-spending special interests are set on a collision course after a group backed in part by California trial lawyers filed more than 800,000 signatures supporting a ballot measure that would significantly increase medical malpractice caps on pain and suffering injuries.

Consumer Watchdog, the group backing the ballot initiative, filed the 840,000 signatures with the Los Angeles County Clerk’s office on Monday. California requires 504,000 valid signatures to place a statute change on the ballot; the Secretary of State’s office will spot-check the signatures searching for errors, but the sheer number of signatures turned in means it’s likely to make the ballot.

The proposal would mandate random drug tests for doctors and require physicians to use a state prescription drug database. It would also index the maximum amount a jury could award a victim of medical malpractice for pain and suffering to inflation, more than quadrupling the damages a victim could receive.

Gov. Jerry Brown (D) signed the original Medical Injury Compensation Reform Act, which capped pain and suffering damages at $250,000, during his first stint as governor, back in 1975, in response to doctor complaints that medical malpractice awards were skyrocketing, along with their insurance premiums. In the intervening four decades, trial lawyers have sought to raise that cap, while doctors have fought to hold the line.

A quarter million dollars in 1975 would be worth $1.1 million today. Inflation means the value of the top award has shrunk significantly; $250,000 in today’s dollars would be the equivalent of $57,600 in 1975.

Supporters of the so-called Pack Act, named for two children hit by a car driven by a man abusing prescription drugs who fell asleep at the wheel, say it is necessary to end doctor-shopping, in which a patient sees multiple doctors in search of prescription drugs. Opponents said it would drive up health-care costs, limit access to doctors and be a net drag on the state’s health-care system.

California doctors already pay out more in medical malpractice damages than doctors in all but two other states. In 2013, California doctors shelled out $274 million in damages, according to a study by Diederich Healthcare.

State Senate President Darrell Steinberg (D) was trying to head off the clash of the political titans by offering a compromise that would raise the cap on damages to $500,000. But negotiations between the two sides ended abruptly on Friday, and Consumer Watchdog went ahead with its initiative. Once the state receives enough valid signatures, a measure cannot be taken off the ballot.

Medical and insurance industries in California have already pledged to spend more than $30 million to defeat the initiative. Trial lawyers, one of the biggest spenders on politics and political campaigns, are likely to spend as much or more to back their proposal.

Both sides have long histories of backing up their big-spending claims with their checkbooks. The insurance industry spent more than $150 million on lobbying in 2013, according to the Center for Responsive Politics; this election cycle alone, the insurance industry has given federal candidates $13.6 million in campaign contributions, a little less than two-thirds of which went to Republicans.

Trial lawyers spend less on lobbying but more on political contributions. This cycle alone, the Center for Responsive Politics reports lawyers and law firms have donated nearly $29 million to federal candidates, about two-thirds of which went to Democrats.

Doctors and health professionals have spent more than $80 million a year lobbying Congress since the beginning of the Obama administration. This cycle, they have donated about $17 million to federal candidates, with about 60 percent favoring Republicans.

And those are just the federal numbers. In the states, where most insurance and malpractice decisions are made, the three powerful industries are spending tens of millions more to advocate their causes.

Ballot measures have become increasingly expensive in recent years as interest groups wage policy fights on television, rather than in the halls of state capitol buildings. After the presidential contest, the second-most expensive campaign waged in 2012 came in Maryland, where supporters and opponents of a proposal to expand casino gambling spent $95 million.

In 2012, the 186 ballot measures in states around the country drew $934 million in spending, an all-time high, according to the National Institute on Money in State Politics. Nearly half of that money, $455 million, was spent on ballot measures in California alone.

Forget the battle for any one Senate seat, or a high-priced governor’s race. Combine multiple big-spending interest groups with a high-stakes change in policy, like medical malpractice reform, in a state known for prolific spending on ballot initiatives, and the result is likely to be the most expensive race of the entire year.