Chuck Todd explains why he thinks Joe Biden (and now Dept. of Education Secretary Arne Duncan) are publicly supporting SSM now:

[The White House is] so sensitive to Biden doing this because, number one, gay money in this election has replaced Wall Street money. It has been the gay community that has put in money in a way to this President that is a very, very important part of the fundraising operation for the President Obama campaign. The second part of this, they are sensitive to the fact that here they have done everything to marriage saying they don’t want to take away anybody’s rights that already have them, but they don’t like the idea that it brings attention to what you were just saying. What Biden has done has brought attention to the fact that the President is not, quote, “there yet.” -- Mediaite