If the Maine Legislature approves same-sex marriage, opponents will try to collect enough signatures to suspend the law until a public referendum can be held -- probably in June 2010 -- asking voters if they want to overturn it. But Mary Bonauto, the lawyer who argued the case that led to the legalization of same-sex marriage in Massachusetts, said gay rights groups would wage an exhaustive campaign against a so-called people's veto.

"I think we have better than a fighting chance on that," Ms. Bonauto said.