A proposed constitutional amendment protecting stem cell research is likely to rise or fall on whether Missourians view a mass of cells in a Petri dish as a cure for disease or a human embryo worthy of protection.

But if critics of the measure have their way, voters this November also will wrestle with an entirely different ethical question.

Brochures mailed in recent weeks to more than 90,000 Missouri homes argue that research protected by the ballot measure would exploit women, luring them into the potentially dangerous practice of egg donation.

The viewpoint has made for strange bedfellows in the stem cell debate, aligning religious groups that oppose abortion with some women's health advocates.

"I can't remember the last time radical feminists lined up with me," said the Rev. Rick Scarborough, a Southern Baptist preacher who heads Vision America, a national group campaigning against the stem cell measure.

Scarborough's comment, made last week at a rally against the ballot measure, drew riotous laughter from the crowd who filled the pews of a Jefferson City church.

But supporters of the stem...