Reports that the Democratic Party may add support for gay marriage to its party platform are in keeping with a significant shift of opinion on this issue among Democrats nationwide.
Just four years ago, in 2008, only half (50%) of Democrats favored allowing gays and lesbians to marry legally, while 42% were opposed. Support for gay marriage among Democrats has jumped to 65% today, more than double the percentage that is opposed (29%). [cont.]
Pew
See also: http://www.pollingreport.com/civil.htm