Sen. Barack Obama today wrote a letter to stating he oppposed a ban on gay marriage.

In a letter to San Francisco's Alice B. Toklas Lesbian Gay Bisexual Transgender Democratic Club, the presumptive presidential nominee said he opposed "the divisive and discriminatory efforts to amend the California Constitution" and similar efforts in other states.

Good on Obama. He's not afraid to change his mind.

Obama is skating gingerly past his previous position on the issue.

The Illinois senator has said repeatedly that he believes marriage should be only between man and a woman. When the California Supreme Court overturned the state's ban on same-sex marriage in May, Obama released a carefully nuanced statement saying he respected the court's decision, believed states should make their own decisions on marriage and "will continue to fight for civil unions as president."

We're behind Obama on this one, all the way.