"In the event of a vacancy, President Obama would have to decide how much of a fight he wants. However, no matter who he appoints, the Republicans will scream that the nominee is a far-left activist judge (unless he or she is an academic, in which case they will scream he or she is a far-left academic). Unfortunately, a rational discussion of the candidate's merits and qualifications isn't possible in the current climate of charges and countercharges. Given that most Republicans in the Senate will filibuster anyone he picks, independent of the person, Obama might just decide to pick a young liberal to fire up his own base, many of whom are disappointed with him for not pushing for a public option in the health-insurance wars. The selection of a young, liberal, woman might get them excited and willing to go vote in November.
Reading the tea leaves on who he might pick is very difficult since it is Obama's decision and his alone. Of course, before picking Sonia Sotomayor to fill David Souter's seat, the Justice Department compiled thick dossiers on multiple potential candidates, so not much research or vetting would be required now. Still, what Obama has to weigh is how much of a fight he wants and how much that fight will distract everyone from his policy goals of reining in the banks and possibly dealing with immigration. He really, really does not want the next six months to be all about abortion.
However, Obama is well known for wanting to change the long-time direction of America rather than winning the 24-hour news cycle. He is keenly aware that Supreme Court appointments are a major tool for doing this and he surely knows the Democrats will probably have only 51-55 votes in the new Senate, as opposed to 59 now, so this may be his only opportunity to name a real progressive." - Electoral-vote.com