The proposal - a public initiative known as Proposition 161 - is similar to one rejected by a margin of less than 6 per cent by the electorate of Washington State last year. After this relatively narrow defeat, proponents of the legislation decided to shift ground to a state with a similar reputation for independent and liberal attitudes. Once again, the rival camps are preparing to do battle.
Californian law already allows people to draw up a document instructing doctors to withhold or withdraw 'life-sustaining treatment', such as intravenous feeding, should they become terminally ill or comatose.
The proposed new law would mean a patient could ask a doctor to administer 'aid-in-dying' - for instance, by lethal injection - so long as two doctors had decided that he or she was incurable and had a life expectancy of no more than six months. Supporters of 'aid-in-dying' argue that modern medical techniques cause terminally ill people to be kept alive against their wishes, resulting in prolonged suffering and an undignified death. The pro-campaign includes the Unitarian Church, several women's and gay rights organisations, and the American Civil Liberties Union.
The proposed law differs from the Washington proposition in several respects. It still states that a patient must be mentally competent when they ask to die, and that they must do so in front of two disinterested witnesses. But the proposition also requires a patient to request death on at least two separate occasions. In order to dampen concern about the risk of pressure on the elderly and impoverished, requests from nursing home patients must also be witnessed by a patients' 'advocate or ombudsman', chosen by the state.
The opponents, who include the Catholic Church, say the planned law lacks safeguards: there is a risk that people will ask to be put to death because they are suffering from depression after learning that they are terminally ill, a diagnosis which could turn out to be wrong. As there is no 'cooling-off period', they could be killed almost at once.
Nor is there any requirement for them to receive counselling before deciding their fate, or even psychological evaluation.
The issue coincides with claims by a coroner's official in southern California that six suicides this year have been linked to Final Exit, the best-selling euthanasia manual by the British author Derek Humphry. But so far, the proposition has been overshadowed by the presidential election and California's recently resolved budget impasse. Both sides expect it to emerge in the next few weeks, and promise to defend their corners fiercely. If it is anything like the Washington ballot, no holds will be barred. Cancer patients, both for and against, took part in television commercials as they sought to win over the voters' hearts and minds.
The only other country where euthanasia is tolerated is Holland, although its use remains highly controversial.
Critics in America point to a recent study into euthanasia in Holland which indicated that fewer than 10 per cent of the cases were reported to the authorities, and that in 1990 more than 1,000 patients were put to death without their consent.
The issue has also attracted additional attention in the US because of the publicity surrounding the methods of Dr Jack Kevorkian, the Michigan doctor who devised - and used - a machine to assist people to commit suicide.