If a bill does get to Gov. Martin O'Malley, he has pledged to sign it. But the story isn't over there. Citizens have the right to petition any act of the General Assembly to referendum, although it happens rarely on statewide issues. A petition would need 55,736 signatures to get on the ballot -- difficult, certainly, but on an issue like this, hardly insurmountable. For context, the petition that put the Arundel Mills slots casino on the ballot collected 22,000 signatures in Anne Arundel County alone (though in fairness, that effort benefited from the backing of the Maryland Jockey Club, which hired professional canvassers).

Opponents of gay marriage would have to submit a third of the signatures, 18,579 of them, by June 1 and the rest within 30 days after that. If they meet those deadlines, the law would be prevented from going into effect until after the public voted on the issue in November. Thus, Maryland would not have a situation like the one in California, in which thousands of same-sex couples were married in the period between a court ruling declaring gay marriage legal and the approval of a voter referendum that outlawed it.