[spatne]

Frist will not be in the next Senate. He's not running for re-election in order to focus on his presidential run. Frist's open seat will be won in November by either Bob Corker (R) or Harold Ford, Jr. (D). Corker probably has the edge right now, but it's a closer race than most people had anticipated. It is certainly within reach for Ford.

Whichever party is in the majority will hold a vote for the new majority leader. Mitch McConnell (KY) is the current majority whip and is probably a good candidate to run for the post. Trent Lott (MS) might try to recapture the post after stepping down due to some unfortunate remarks he made at a function for Strom Thurmond. Rick Santorum (PA) is also in a power position, but his re-election bid is in big trouble as he's getting trounced by conservative Democrat Bob Casey, Jr.

If Democrats take control of the Senate, I assume that minority leader Harry Reid (NV) would get the job. I can't think of anyone who would/could mount a serious challenge at this point.