The question of which came first has to be boil down to when there are published accounts of either of the Cheney parents espousing that people who engage in homosexuality should be marrying and whether those accounts pre or post date the Cheney daughter’s behavioral choice.
According the Wikipedia article about the daughter, it was she who encouraged her father to support marriage by people engaging in homosexuality. http://en.wikipedia.org/wiki/Mary_Cheney
That explicit reported information, if true, and it does seem quite plausible and likely, suggests to that he had a different point of view prior to his daughter’s influence - and that is my general point about these politicians who do an about face when it’s their kid who goes against the tenets of their families and the fabric of Judaeo-Christian society.
It’s hard to know what is in your mind with your tiny little obsession, there is no point to it.
Fifteen years of supporting gay marriage is sufficient, if you want to try and figure out if he had ever formed an internal political position on it before he learned that his daughter was a lesbian, you should do that, it is of no interest to me.
You can waste all of your time that you want, trying to read those meaningless tea leaves.
If a professional politician wanted to run a republican presidential campaign on promoting gay marriage, almost a decade and a half ago, then that man sounds like he was open to the idea once it first arose in America.