If I had to guess at this point, I'd say that by tomorrow there will be numerous columns emanating from Washington saying that President Obama needs to pick a "consensus" nominee for the Court, or risk doing more damage to his party before the midterm elections. And as usual, the Washington consensus is wrong, for moral AND political reasons.
Let's be clear about one thing. During past debates over Supreme Court nominees, replacing a liberal with a liberal or a conservative with a conservative has been considered entirely appropriate amongst mainstream thinkers. If President Obama chooses to replace a liberal with another liberal, he would be following the normal Washington playbook. A President trying to truly right the balance of the Court might consider finding a jurist even more liberal than Stevens. The man was appointed by Gerald Ford afterall! But let's be realistic for a second.
What I worry about this time, is that "mainstream" voices may completely loose what little grasp they may have on reality by criticizing the choice of a Liberal. They would cast the alternative as a "centrist" choice, which of course is a misnomer. I won't present my thesis here about how far right things have shifted since FDR, but I will point out that the mainstream Washington-centric crowd has been drinking the Kool-Aid for some time now. Remember how the non-single payer health care bill was part of the "liberal agenda?"
Any how, let's just see what happens. It's a bright line test for a group that has clout in politics, even though they often do not deserve it.