Obama's embrace of marriage equality is solidifying the party line:

Retiring gay Rep. Barney Frank (D-Mass.), who sits on the committee, told the Washington Blade on Monday that the 15-member panel unanimously backed the inclusion of a marriage equality plank after a national hearing over the weekend in Minneapolis, in which several witnesses testified in favor of such language. … A DNC staffer, who is familiar with the process and spoke on condition of anonymity, said the language in the platform approved on Sunday not only backs marriage equality, but also rejects DOMA and has positive language with regard to the Employment Non-Discrimination Act.

More evidence of the president's rhetorical impact here, here, here and here.