Senator Tim Johnson, (D-SD) is right now undergoing brain surgery for something. It was intially reported as a stroke, then as not a stroke, but now is apparently something serious enough to require emergency brain surgery in the middle of the night.
First of all, I am praying both for Sen. Johnson and his family at this difficult time. With conflicting reports out, the only thing that we can say for sure is that it will be some time, at least a day or two, before we know exactly what this is and how serious it is.
In the event that Johnson is unable to continue his service in the U.S. Senate, then South Dakota Governor Rounds, a Republican, will appoint his replacement. Rounds will appoint a Republican, as is his right, and it will, if it happens, undo one of the main results of the elections. In a year when more Democratic Senate seats than Republican seats were up for election in the Senate, Democrats managed to win six seats (including two by a combined 9,000 vote margin) and complete an improbable takeover of the Senate. With Justice Stevens' heart problems, this is of critical importance. Without it, it is conceivable that President Bush could appoint a fifth 'strict constructionist' justice to the Supreme Court and radically alter the direction of the court (which is now split 4-1-4, with Anthony Kennedy the center of the court.)
Now, I don't blame the GOP if they get the opportunity, for seizing it. Democrats would do the same. In fact, a few years ago, Paul Coverdell, a Republican Senator from Georgia died tragically in the middle of his term, and then Democratic Governor Roy Barnes selected a Democrat to replace him (though I would question Barnes' judgement in the matter; he selected his predecessor in the Governor's mansion, Zell Miller, who in his relatively brief stay in the Senate rarely voted with other Democrats and used his position to bash them, even going so far as to endorse President Bush for re-election.)
If there is a silver lining it is that even if the Senate becomes 50-50 with Dick Cheney breaking the tie and returning power to the Republicans, it will be moved much to the left from where it was, and Democrats will only need to convince a single Republican to join them (plus keep Joe Lieberman and Ben Nelson in line) in order to block anything. But that is still a lot different from having control.