I'm a sucker for YouTube videos of politicians who once opposed gay marriage explaining why they have changed their minds. It's a little genre that, happily, is growing.

These accounts tend to follow a pattern. They are often emotional. They almost always reference gay family members, co-workers, or friends -- people whose desire to be accepted as equal activated in the hearts and minds of these politicians the notion, seemingly obvious once it is articulated, that a legislative prohibition on same-sex marriage is discrimination akin to Jim Crow.

One of my favorites is the five-minute speech of Republican San Diego Mayor Jerry Sanders, who ran for office on a platform of opposing gay marriage. In 2007, he tearfully announced his support for a city measure supporting gay marriage:

I have close family members and friends who are members of the gay and lesbian community. Those folks include my daughter Lisa as well as members of my personal staff. I want for them the same thing that we all want for our loved ones: for each of them to find a mate whom they love deeply and who loves them back. . . . And I want their relationships to be protected equally under the law. In the end, I couldn't look any of them in the face and tell them that their relationship, their very lives were any less meaningful than the marriage I share with my wife.

Earlier this year, Washington Governor Christine Gregoire announced her support for a bill legalizing same-sex marriage in her state. Her speech was a compelling, and largely dispassionate, argument in favor of marriage equality. It was not until the end of her press conference, when she recounted her previous opposition to gay marriage, that the emotion came through:

It was my children, it was the children of friends, it was friends, it was leaders ... that I finally said to myself, it's time to do the right thing, and let me just tell you, I feel so much better today than I have for the last seven years.

Republican Minnesota State Rep. John Kriesel's conversion on the issue came after a near-fatal accident while serving in Iraq. Lying on the ground, looking at his mangled legs, and thinking he was going to die, he was a changed man:

It made me think about this issue. And say, 'You know what, what would I do without my wife?' She makes me happy. Life is hard. . . . Happiness is so, so hard to find for people. So they find it, they find someone that makes them happy, and we want to take that person away. We want to say, 'Oh no, you can be together, you can love that person, but you can't marry them.' You can't marry them. That's wrong. That's wrong and I disagree with it.

These politicians appear to be thoughtful people who had a block preventing them from seeing the discrimination inherent in same-sex marriage bans. When that block is removed, we see genuine emotion that politicians rarely express. They realize that, as President Bill Clinton explained in 2009, they were hung up on the word "marriage" and what it traditionally meant:

I realized I was over 60 years old, I grew up in a different time, and I was hung up about the word. I had all these gay friends, I had all these gay couple friends, and I was hung up about it, and I decided I was wrong.

For those of us whose support for gay marriage is reflexive and uncomplicated, it can be a struggle even to understand the opposition. Why do they care, we ask. What's it to them if gay people get married? To me, what these videos reveal is that many politicians seem to oppose gay marriage because they think most of their constituents do (so it's good politics), and because that's all they've ever known. It doesn't strike them as something even worth agonizing about. But then something happens; something opens their eyes and they see, they feel, what it means to tell two people who are in love with each other that they are not allowed to get married. That's why these videos are emotional: there is shame for past behavior; relief at the awakening of enlightened views; and gratitude for the opportunity to chart a different and better course.

And you know what? It doesn't work the other way. I scoured the internet and could not find a single video of a politician who once supported gay marriage and now opposes it. I'm sure such people exist (and Mitt Romney may be one of them). But few people wake up and realize they have been treating folks with too much respect, too much dignity. No, this is a march that is headed -- slowly, and with setbacks, to be sure -- in only one direction: towards equality. And that's fun to watch.