Billions have been spent on California’s
 ballot measure battles. But this year is
 unlike any other

Until this year, the top spot belonged to a high-stakes battle between labor unions and business groups that spanned two ballot measures in the 2012 midterm elections.

Proposition 30, championed by then-Gov. Jerry Brown, aimed to raise income and sales taxes with promises that it would help fund education. The powerful California Teachers Assn. enthusiastically endorsed the plan.

The teachers union also spent heavily to defeat another proposal that fall, Proposition 32, which aimed to dilute the heft of labor groups like the CTA by barring union members' dues from being used to fund political campaigns.

Conservative billionaires bankrolled a little-known group, the Small Business Action Committee, on the other side. Charles Munger Jr., a wealthy state GOP activist, contributed more $30 million. Another $11 million came from a shadowy Arizona-based group hit by a massive fine after an investigation revealed the money’s undisclosed connection to billionaires Charles and David Koch.

Labor groups and Brown prevailed at the ballot box when Proposition 30 passed and Proposition 32 failed.

Four Southern California tribes spent heavily to protect an expansion of gambling approved the year before. Opponents — including racetrack owner Terrence Fancher, casino workers’ union Unite Here, and two competing tribes — gathered enough signatures to put four measures on the ballot aimed at rolling back the growth of the gaming outlets.

All four measures passed with similar support, allowing the gaming agreements to move forward.

Proposition 87 would have imposed a tax on oil production to fund alternative energy research. The initiative was the brainchild of the late Hollywood producer Stephen Bing and became a cause célèbre among tech billionaires.

Chevron and Aera Energy, a company jointly operated by Shell and ExxonMobil, led a successful campaign to defeat the measure.

Proposition 8 sought to limit the profits of the kidney dialysis industry by requiring clinics to give rebates to insurers and pay a new tax on revenue.

The Service Employees International Union-United Healthcare Workers West, which aims to organize the dialysis industry, sponsored the measure and contributed most of the $19 million raised to pass it.

DaVita and Fresenius Medical Care, which combined control 75% of the industry in California, bankrolled the successful opposition campaign.

Undeterred by failure, labor groups pushed a similar measure onto the ballot this year, and the same protagonists are waging another expensive fight over the future of the dialysis industry.

Amid a national debate around rising drug costs, Proposition 61 sought to lower how much California agencies pay for prescription drugs. The measure would have barred state government health programs from paying more for these drugs than the U.S. Department of Veterans Affairs, which typically pays less than most health providers.

Leading the fight to vote “yes” was the AIDS Healthcare Foundation, which contributed more than $18 million, and Vermont Sen. Bernie Sanders, who endorsed the measure.

Pharmaceutical companies amassed more than $100 million to defeat the measure and were successful.

Proposition 56 raised cigarette taxes by $2 a pack to fund increased spending on state healthcare services.

Its financial backers were led by billionaire Tom Steyer, who briefly ran for the 2020 Democratic presidential nomination. In a sign of how public opinion had turned against the tobacco industry, business groups other than cigarette manufacturers sat out the fight.