Proposition 45 would give California's insurance commissioner the power to reject health insurance rate hikes found to be excessive.
The measure has sparked strong opposition from California's biggest insurance companies.
Kaiser, Wellpoint, and Blue Shield lead the pack. Along with the insurer Health Net, the companies contributed more than $12 million to defeat the measure over the last week.
Opponents have raised a total of more than $55 million, and are running TV ads statewide.
Supporters, led by the non-profit Consumer Watchdog, have raised about $2.5 million. Jamie Court, the group’s president, said they spent most of that money qualifying the measure for the ballot.
"And we’re hoping to get some more money in the last days, so we can do a very little bit of targeted advertising in LA County," Court explained. "But we’re not going to be doing it anywhere else in the state, because we don’t have the money.”
The No on 45 campaign, on the other hand, said it’s planning to spend a lot of money in the last two weeks to reach as many voters as possible.