One of the reasons that some people are stated to be preferring Democrat over Republican party when voting is the fact that the former are perceived as supporting gay marriage, while the latter typically strongly oppose it.
(I'll leave aside the fact that Pres. Obama shared GOP's opinion on the topic till 2010 :)
But how much of an issue is it electorally?
More specifically, are there any research/polls/surveys that try to estimate how much of an electorate is lost to GOP on the margin because of same sex marriage issue?
In other words, the poll/survey would ask something similar to "If in the next election, GOP platform officially supported same sex marriage, would you change your vote from DNC to GOP" if all other positions stay the same? (And vice versa, how many people would stop voting "R" if such a change happened)?