You could have fooled me. Where is the source for that? Do you have a link?
There are several links, including Free Republic, that state that at least half (if not a majority) of Kerry supporters oppose Gay Marriage.
But Kerry himself supported Gay marriage, and by association, so did whomever voted for him.
That's why I take most polls with a grain of salt.
The last elections. In every state, the percentage who voted against gay marriage was FAR above the percentage who voted for Bush. That means a lot of Kerry voters voted down gay marriage as well. (Not to mention a few - although not very many - Bush voters may have voted in favour of gay marriage, mostly ultra-libertarians)