Republican have a relatively clear path to 48 seats, and probably a somewhat better than 50-50 shot of defeating Giannoulias in Illinois. The California, New York, Washington and Wisconsin seats remain longshots, and most of that shot is entirely dependent upon the GOP’s ability to get their preferred candidate in place.

If the GOP does manage to get to 50 seats, then another variable enters the picture: Joe Lieberman. Would Lieberman caucus with the Republicans in order to deny the Democrats a Senate majority? He’s made noises about running as a Republican in 2012, so it is certainly possible.

Bottom line, control of the U.S. Senate looks likely to be in play come election day in November.