As they have for more than five decades, California voters overwhelmingly support the death penalty - but in a marked shift, more voters now prefer that convicted murderers be sentenced to life without parole instead of death, according to the latest Field Poll.

The survey, conducted this month, comes as criminal-justice-reform advocates are gathering signatures for a 2012 ballot measure that would ban capital punishment in California.

The poll shows they have their work cut out for them: A solid 68 percent of voters favor keeping the death penalty, with conservatives overwhelmingly in support and nearly half of liberals opposed. But for the first time since the poll began asking the question 11 years ago, more voters - 48 percent - say they would prefer that someone convicted of first-degree murder serve life without the possibility of parole. Forty percent prefer the death penalty.

Field Poll director Mark DiCamillo noted that 11 years ago, 44 percent of those polled said they preferred death as punishment for first-degree murder and only 37 percent in favored life in prison. Last year, it was nearly evenly split.

But this year, the debate has gathered steam in California and elsewhere. The recent execution of a Georgia man many believe was innocent reignited the debate nationally, and executions have been on hold in California since 2006 because of a lawsuit challenging the state's lethal injection method.

Forty-three percent of voters surveyed by the Field Poll said they think the death penalty is cheaper than life imprisonment, while 41 percent think it is more expensive.

A recent study, however, found that maintaining the death penalty costs $184 million a year more than it would cost taxpayers to simply leave the state's condemned killers in prison for life. The higher cost is largely the result of legal fees associated with death sentence appeals. The same study found the average execution takes place 25 years after conviction.

The Field Poll also found that a majority of voters, 52 percent, believe that innocent people are executed so rarely that it is "unimportant"; that voters are nearly evenly split on whether a life without parole sentence really means someone will never get out of prison; and that by a 45 to 41 percent margin, voters believe that minorities are no more likely to receive the death penalty than whites.

How voters answer those four questions is directly tied to whether they support life in prison over death, DiCamillo said. But overall, he said, voters are far more skeptical of capital punishment than they were two decades ago.

"There has been a change in attitude," he said. "Twenty-two years ago, the death penalty side argument prevailed by a large majority - now voters are divided in their opinions on many statements, including the cost of death versus life in prison, does a life sentence actually guarantee they will stay in prison, whether innocent people are executed, and their views of how it is administered to the ethnic population."

The telephone poll had a margin of error of plus or minus 3.2 percentage points and was conducted between Sept. 1 and 12 among 1,001 registered California voters.