An extreme radical like Van Jones or Eric Holder would never get through the confirmation process - even the weak-kneed Republicans (and moderate Democrats) would fight that. However, in all likelihood, the weak-kneed Republicans won't fight a nominee of the President of their party and the Democrats will fall in line since they are getting someone with a similar ideology. With either Romney or Obama will probably get a Kagan or Sotomayor.
We need to pray that the four conservatives (and Kennedy) on the court stay healthy until the next bleak four-year period ends. The problem is that if Romney wins, he'll probably run for a second term (effectively freezing out a conservative alternative), so the bleak period will last for eight years (either eight years of Romney or four years of Romney followed by four years of the new Democrat President).