Why Constitutionalist justices matter, and are the only ones truly capable of carrying out their mandate under the Constitution.
President Obama will likely nominate a candidate with a history of judicial activism. When the Senate initially rejects this nominee, he will call them obstructionist. He and much of the media will claim that they are attempting to deny him his Constitutional rights. Of course, this will be after he has exercised precisely that, his right to nominate a replacement for Justice Scalia.