Why is the subject "Gay Marriage" at all? Most people (including me) don't care about gay marriage - it is not what this election is all about. National Security and the economy are the two big issues in this election - and Bush/Cheney are the best men for the job in that respect.
Because this election is a contest between those who want America to be culturally and politically part of Europe ("international law", UN based foreign policy, secularist cultural values) and those who don't (unilateralism, religious based value systems).
Actually, you answer your own question. Yes, National Security and the Economy are the big issues and they are Bush/Cheney strengths. Thus to focus elsewhere is the goal of John-John and the media that supports them.