With a McCain victory, this new conservative bent of the Supreme Court would almost certainly be even stronger - especially considering that the judges likely to retire are all in the liberal minority.
The next appointment to the court will almost surely fill the seat now held by one of the court's liberals, whose average age at the beginning of next October's term will be 75. For Obama, any initial appointment would likely replace one liberal with another, albeit with a younger and perhaps more outgoing advocate for his views of the court's role.
But a McCain victory could give the conservative bloc a clear-cut majority for years to come. President Bush has provided the model with his nominations of Roberts, to continue the conservative legacy of former chief justice William H. Rehnquist, and Samuel A. Alito Jr., to replace the former justice found most frequently in the middle, Sandra Day O'Connor.
On the other hand, with an Obama victory we would be chosing a President with an exceptionally strong understanding of our Constitutional rights and values (remember, he was a civil rights lawyer and constitutional law professor for many years in Chicago) and has a consistent track record on civil liberties.
I don't know about you, but if I weren't already excited about his personal qualities and his sound policy proposals, that alone would be enough to make me excited about voting for him.