Here is the plank from the platform for this year. There is no question that president Obama supports gay marriage.
"Freedom to Marry. We support the right of all families to have equal respect, responsibilities, and protections under the law. We support marriage equality and support the movement to secure equal treatment under law for same-sex couples. We also support the freedom of churches and religious entities to decide how to administer marriage as a religious sacrament without government interference.
"We oppose discriminatory federal and state constitutional amendments and other attempts to deny equal protection of the laws to committed same-sex couples who seek the same respect and responsibilities as other married couples. We support the full repeal of the so-called Defense of Marriage Act and the passage of the Respect for Marriage Act."
The language in this plank seems to oppose any legislation banning gay marriage but does not openly support anything other than civil union.
It really doesn't matter. People seem to vote the way their parents did.