Four years ago we voted for John Kerry, despite being at odds with him policy-wise on many issues and being generally underwhelmed by him personally. As it turns out, George Bush got himself elected and in 2005, had the opportunity to nominate two Supreme Court justices to replace the retiring Sandra Day O'Connor, moderate, and William Rhenquist, not moderate. With the nomination and eventual appointment of John Roberts and Samuel Alito the Court lurched rightward. That's kind of what we were afraid of. But really, all that happened was one moderate got replaced by one conservative.
Obama could possibly have the opportunity to nominate three Supreme Court justices, all potential liberal replacements.
The average Supreme Court tenure is 26 years So thank goodness for 2008. Had Sarah Palin been elected president, there's no telling how far right the SCOTUS would drift and for how many years to come.