Because 1: to do such a thing would be morally wrong, and 2: it would be perceived by the public as a polular president using that popularity to prop up cowardly, sniveling idiot and political opportunist...and the public would be absolutely right.
People have tried to defend him. People have tried to throw him a proverbial rope to pull himself out with, and he hasn't taken any opportunity he's been given. This is Lott's mess. Let him clean it up.
Why shouldn't they use the race card again? It works so well on all of you. No need to wait for the other side to crucify him we do that all by ourselves.