Speaking of that, if SCOTUS does legalize Marriage Equality in 50 states There will be pressure from the Religious Right on Congress to pass the Federal Marriage Amendment.
I Don't think this will be a problem for the House GOP. But I bet most of the GOP Senators ( many of them up for election in 2016) would rather not have to take that vote.
So what will the Senate Majority Leader do?
I imagine McConnell will just ignore it. That being said, it's not like such an amendment could ever get 290 votes in the house and 67 votes in the senate (both of which are required to send an amendment to the states for ratification). Not to mention that the sort of amendment the religious right wants (no gay marriage, no civil unions, nothing) isn't even popular in the south these days - PPP has consistently found that even in southern states that still have majority SSM opposition, there is still usually majority support for civil unions.
