Opponents of gay marriage have been aggressive _ and in most cases successful _ in passing measures to block gay marriage in the states expected to be at the heart of the race for the White House. Actions in the past decade in the states considered to be as 2012 toss-ups:
COLORADO: Voters passed referendum in 2006 banning same-sex marriage. This week, Democratic Gov. John Hickenlooper recalled legislators to consider legislation allowing civil unions.
FLORIDA: Voters passed referendum in 2008 making state-recognized marriage between a man and a woman.
IOWA: Iowa Supreme Court in 2009 unanimously struck down the state's statutory ban on gay marriage. Opponents of the decision mounted campaign that ousted three of the justices in 2010 retention vote.
NEVADA: Adopted constitutional amendment in 2002 banning gay marriage.
NEW HAMPSHIRE: Legislative effort failed narrowly in Republican-controlled legislature this year to repeal 2007 legislation allowing state-recognized same-sex partnerships.
NORTH CAROLINA: Referendum passed Tuesday by wide margin banning gay marriage.
OHIO: Passed referendum in 2004 banning gay marriage.
VIRGINIA: Ratified constitutional amendment outlawing gay marriage in 2006.