Stuart Taylor has the doomsday scenario:
July 1, 2008 -- With the retirement of 88-year-old Justice John Paul Stevens today, the Supreme Court's membership dwindled to four. The remaining two liberals (Stephen Breyer and David Souter) and two conservatives (Antonin Scalia and Clarence Thomas) are almost certain to deadlock on big issues including abortion, affirmative action, gay rights, religion, and presidential war powers. So any tie-breaking replacement for Stevens would be in a position to rewrite vast areas of constitutional law.Unlikely, sure -- but what's the alternative? A wishy-washy court of sensible moderates? Nine Steve Breyers? No thanks.
(Link via RCP.)