I hate to get involved in such a pointless conversation, but Alan, you are thinking about this way too much. I don't think anyone really cares. Or should I say the amount of people in this country that would vote against mayor Pete just because he is gay is probably just as large as the amount of people who voted against Obama because he was black. Frankly, there are probably some, but not enough to make a difference.
Second, every gay couple I know refers to each other as husband and every lesbian couple I know refers to each other as wife. There are no specific roles they happen to play, or at least I have never met a couple that has.
The only time where gender roles may be important would be if the couple was raising a child. Men and women raise and interact with children differently, and there is a lot of evidence children need both types of parenting to develop properly. In this instance, there may be a need to decide who plays what role, but beyond this, it does not matter. I don't believe Mayor Pete has any children, so this does not apply to him anyway.
Last, for the love of God, can we stop using the word partner for anything else then business partner! We are in the 21st century, just say husband or wife (or boyfriend or girlfriend). Saying partner just confuses the hell out of people, especially for people like me who happen to work a lot with business owners.
One of my clients is a firm owned by two women and whenever I refer to them as partners to someone new, I get blank stares and need to both explain that they are not lesbians (and are actually married to their own husbands) and that, just like men, women can form partnerships too. It is quite annoying.