To be clear, Sandoval has not come out in favor of Same Sex Marriage. In fact in his legal brief to the court last month (Sandoval is named in the suit) he defended Nevada's SSM ban “because it serves the legitimate purpose of preserving traditional marriage.” He also released a statement in January saying:
What has happened since is that his AG has looked at the case and at other rulings by the Appeals Court and come to the conclusion that they are going to lose the case and Sandoval agreed. He is just accepting the reality that there is no legal basis to "preserve traditional marriage."
There are many other states that are defending their SSM bans in Federal court, but at this point they are mostly focusing on the dubious legal argument that banning SSM is needed in order to perpetuate "responsible procreation" which is a term that essentially means that opposite sex couples need marriage as an incentive in order to have planned children, but SSM couples do not need marriage because any children they have will be planned. It is of course a ludicrous argument, but it all the anti-SSM people have for now.
It appears Sandoval and his AG chose not to go down the "responsible procreation" road as it is laughable. In fact
when it was used in the Prop 8 case with the SCOTUS it actually drew laughter and mockery, even from Scalia.
Here are parts of the exchange between the justices and the lawyer defending Prop 8 (Cooper):
