OLYMPIA, Wash. — The emotionally charged battle over end-of-life decisions has taken to the airwaves as Washington state voters decide whether to allow doctors to prescribe lethal medication to terminally ill patients.

Recent TV and radio ads by opponents feature actor Martin Sheen, who calls the measure a "dangerous idea" that could be used by the most vulnerable in society. Supporters are on TV with an ad spotlighting a widow who says it lets those who are suffering have control over their final days.

With both sides having raised a combined $3.5 million, much of it still unspent, more ads are expected in the coming weeks.

The measure would allow physicians in Washington state to help terminally ill patients end their lives. Oregon, where voters first approved the idea in 1994, is the only state with such a law.

A recent poll by independent pollster Stuart Elway found that the measure was popular, with 57 percent of voters polled supporting it and 33 percent opposed. That poll, conducted in September, showed 10 percent still undecided, while 16 percent were leaning 'yes' and 10 percent were leaning 'no.'

"It really is a matter of personal decisions and having the freedom to make your own decisions about end-of-life care," said Anne Martens, spokeswoman for Yes on I-1000.

Todd Donovan, political scientist at Western Washington University, said he wasn't surprised that Initiative 1000, also known as the "Washington Death with Dignity Initiative," is polling well.

"There is that libertarian streak in the northwest that it sort of taps into," he said.

The measure is strongly opposed by religious groups, and Catholic Church officials said their opposition shouldn't surprise anyone.

"Our teaching has always been in favor of life," said Sister Sharon Park, executive director of the Washington state Catholic Conference. "The purpose of law is to protect, and this certainly does not protect the vulnerable."

Outside of Oregon, advocates of the idea haven't fared well. California, Michigan and Maine voters rejected the idea, and bills have failed in statehouses around the country. In Washington, voters rejected physician-assisted suicide in 1991.

This year's proposal differs in that it would not allow doctors to administer lethal drugs on behalf of patients who couldn't do so themselves.

Initiative 1000 mirrors the Oregon law, which took effect in 1997 after a lengthy court fight, and would allow the terminally ill to obtain lethal prescription drugs for ending their own lives.