Mustang Bobby has a theory on the about-face.
So why the sudden switch? A couple of reasons come to mind. First, he's going after the moderate to progressive voters that are not completely sold on Kendrick Meek, the Democrat in the race; second, he sees that DADT repeal is moving through Congress and it polls very well (some give it a 75% approval rating), thereby making it a safe place to be since he's not worried about pissing off the right-wing base any more. And if Sen. Ben Nelson (D-NE) is in favor of it, that makes it okay to go there.
That it might actually be the right thing to do for gay and lesbian soldiers who want to serve their country without living a lie probably never crossed his mind.
Meanwhile, GOP congresscritter Connie Mack makes a conservative case against Arizona's dumbass immigration law.