You speculate. Let's say that the current President Bush has to deal with a rabidly Rat Senate after this election, heaven forbid. Stevens croaks, he has to make an appointment. He tries a solid conservative, gets batted down. So---he finds a moderate, but a much older one, hoping that maybe in five or ten years his party gets control of the Senate again.
Hopefully, future Republican Presidents will have learned from Ford's mistake and act accordingly.
Yeah, that is what I would do if I were the President. Let's hope Karl Rove advise him on that, shall Democrats control the Senate. (Actually, I doubt that they will actually take over, but it will probably be a de facto Democratic Senate with 49 Senators plus a few RINOs that we can't seem to shake)