Polls show a majority of Republicans/Conservatives support gay marriage. They overwhelmingly oppose discrimination against gays in the workplace and favor repeal of Don't Ask Don't Tell. When you look exclusively the religious right, the support for gay marriage drops to 41%, but that is still very significant.
www.cato.org/publications/commentary/is-gop-deeply-antigay-hardly

Its only a matter of time before the states legalize gay marriage and this issue will be behind us. Federal legislation is not necessary because DOMA is already unconstitutional so gay marriage has nothing to do with Congress, Obama, or Romney.