Romney on the other hand supports a constitutional amendment to ban gay marriage. So as it can be seen this is a very divisive issue in the election. But the Republicans don't want to talk about it. Why? because they have nothing to gain but the support of their base. The Republicans would rather continue the discussion on the economy where their Republican candidate is for some reason according to some polls better to handle the economy.
I say all in all the election won't be effected much by this, but the big win I take away from this is Americans are becoming more tolerant of having people of the same sex marry each other. In Canada gay marriage has been legal for quite some time now, and well the sky hasn't fallen down!
Sixty percent of Americans polled were unchanged in their support of the president after he publicly backed same-sex marriage.Read more here