Health insurance premiums have gone up 172 percent since 2002, according to the California HealthCare Foundation. That's what prompted supporters of Proposition 45 to put their measure on today's ballot.

The measure would give California's insurance commissioner the authority to reject health insurance premium increases found to be unreasonable. Proposition 45 would also require insurers to publicly disclose and justify any rate increases.

Waning Support

The latest Field Poll, released Friday, shows 36 percent of likely voters are in favor, 42 percent are opposed, while 28 percent remain undecided. Support for Proposition 45 has sharply declined since early July, when 69 percent of likely California voters were in favor of it.

Who supports Proposition 45 and why?

The measure's chief sponsor is the nonprofit group Consumer Watchdog.

Jamie Court, president of Consumer Watchdog, said the measure would fill a major loophole in the Affordable Care Act.

“There is no governmental body in California or federally that has the power to tell health insurance companies they’re charging too much," he said. "And yet, the health insurance companies sell policies, and we all have to buy them. So, the missing link in the Affordable Care Act is having some kind of mechanism to make sure that health insurance rates are affordable.”

Currently, auto insurance and homeowners insurance companies must get permission from the California insurance commissioner before they can raise rates. Court said Prop. 45 would simply put health insurance under the same system.

Who opposes the measure and why?

A coalition called Californians Against Higher Health care Costs is leading the charge against Proposition 45. The coalition includes health insurance companies, the California Chamber of Commerce, and the California Medical Association.

Opponents raised more than $37 million to fight Proposition 45.

San Diego pediatrician Sherry Franklin, a member of the CMA board of trustees, said the Affordable Care Act is designed to provide consumers some relief for high health insurance costs.

“And I think we need to let the system play out before we start throwing more pieces into the mix," Franklin said. "We’ve created a system; it’s brand new. Let’s let it do its job before we assume that it’s not going to work for us.”

In addition, Franklin said Proposition 45 would give one elected official in California too much power over the health insurance industry.