Poor Bill Frist. Caught between a Bush and a hard place. Now he's not even sure he can bring Social Security to the floor before 2007, which is congressional code for "never".
That, as the Bush Administration surely realizes, is the problem with promoting a nobody who wants to be president. His first allegiance is to his ambitions and not your priorities. Not only would Frist rather not be identified with a stunningly unpopular plan that either fails to pass (still can be used against him, though!) or gets jammed down Congress's throat, but he'd also prefer not to preside over a midterm whupping, where his side loses a bunch of seats (thanks, again, to Social Security) and he, as Senate majority leader, gets to share in the blame. After all, he's only got to keep his stock up for a few more years and then he's on the campaign trail and can stop paying attention. That the president who promoted him is determined to go down in history as the guy who knifed the New Deal, probably bringing Frist down with him, is a real kink in that timeline. But when Senators face a problem, they know exactly what to do:
Stall.