Massachusetts Congressman Barney Frank is predicting that President Obama will drop his legal defense of “Don't Ask, Don't Tell” if legislative repeal fails.

The Senate appears poised to follow in the footsteps of the House and repeal the law that prohibits gay and bisexual troops from serving openly. Four Republicans are expected to side with all but one Democrat, West Virginia Senator Joe Manchin, during Saturday's vote.

But if repeal fails, Frank predicted the president would stop fighting the law in the courts.

“He [Obama] will drop his defense of it because the argument has been, 'Well, you're the president and you have this obligation,' and I think that's generally right, we don't want the president picking and choosing what laws they defend in court. But this one will have lost its legitimacy, its moral legitimacy, its majoritarian claim. It won't be a case anybody could argue with the courts, overturning the will of the voters. The voters – majorities in the House and Senate – have said, no more of this,” Frank told MSNBC's Keith Olbermann.

In October, a federal judge found the policy to be unconstitutional and ordered the military to end its enforcement. The Obama administration convinced an appeals court to put the order on hold.