California voters cooled to a pair of controversial ballot measures over the summer.

Despite relatively low levels of campaigning, support for the health-related propositions 45 and 46 — among the most expensive ballot measures nationwide — fell by double-digits, according to a new poll.

Each measure saw support among likely voters nearly halved between a first round of polling in late June and early July and a second round in late August and early September, according to the Field Poll. Support for 45, which would require health insurers to run rate changes by a state insurance commissioner, was down from 69 percent to 41 percent. Support for 46, which would require random drug tests of doctors and raise some malpractice award limits, fell from 58 percent to 34 percent. In both cases, opposition grew some, but the share saying they were undecided more than doubled.

Early and active campaigning by opponents may have influenced the results, says Jamie Court, president of Consumer Watchdog, an advocacy group that has contributed millions of dollars in support of both measures, according to a Monday count by the edited political encyclopedia Ballotpedia. It’s like being “in a game and the other side’s at bat for a few innings and you haven’t been at bat,” he says. Court also questions whether voters are fully aware of the issues yet and whether the polls are truly comparable given their different sample sizes. “It’s a very odd poll,” he says.

Mark DiCamillo, senior vice president of the Field Research Corp., which conducted the poll, says it’s true that the sample size of 467 likely voters is several hundred shy of the group size from the previous poll, but that shouldn’t make much difference.

“That is true, but it’s still in our judgment a very good sample of likely voters as we know them in each poll,” he said.

There are some noteworthy differences between the two polls, though. The first version did not use the ballot language, which was at that point unavailable. The most recent survey did. Also, the poll questions were asked in different contexts. In the earlier poll, the questions about Prop. 45 were preceded by others about Obamacare, DiCamillo explained in a Thursday e-mail to Harvey Rosenfield, founder of Consumer Watchdog. In the current poll, they were preceded by questions concerning preferences for governor and other statewide positions, again closer to how they might appear on the ballot.

More voters than usual say they’re undecided on a slew of issues, DiCamillo noted. “This indicates to me that voters haven’t really been giving a lot of attention to this year’s election,” he wrote in the e-mail to Rosenfield.

Opponents to both measures have also outraised supporters more than sevenfold. Consumer Watchdog’s $4.6 million in campaign cash accounts for nearly all of that pledged in support of Proposition 45. Opponents have raised $37.6 million. Consumer Watchdog’s support accounts for more than a fourth of the $7.8 million pledged in support of Proposition 46, though opponents have raised $56.4 million.

The groups fighting Proposition 46 represent insurers and doctors, who chafe at the prospect of potentially increased rates to cover larger malpractice losses and drug-testing requirements. Those fighting Proposition 45 are largely health insurers, the industry the measure seeks to further regulate. Consumer Watchdog is joined in its support of the malpractice measure by trial attorneys who stand to get a larger slice of the bigger malpractice awards.

Supporters of Proposition 46 have created a trio of musical ads, such as the one above.