good evening from washington. with advertisers fleeing his radio show over the weekend on saturday, rush limbaugh did something he absolutely never does. he issued a written apology. this time to sandra fluke, the georgetown student he called a slut and a prostitute on his show last week, realizing that that wasn't good enough to preserve his advertising-driven income of more than $50 million a year. rush limbaugh began his radio show today with an explanation and his version of an apology. >> this is the mistake i made. in fighting them on this issue last week, i became like them. against my own instincts, against my own knowledge, against everything i know to be right and wrong, i descended to