Californians voted Tuesday to spend 3 billion dollars on stem cell research, placing the state at the forefront of a research field opposed by conservatives and the Bush administration. Backers of California's Proposition 71, which will support human embryonic stem cell research, said the measure was needed because the Bush administration has restricted funding to about 25 million dollars a year. The campaign became a battle of Hollywood stars after California governor Arnold Schwarzenegger broke Republican ranks to line up his support for stem cell research, together with the late "Superman" actor Christopher Reeve and "Family Ties" actor Michael J. Fox. Actor and director Mel Gibson was among high-profile opponents of the measure.