I finally heard a rationale for McConnell's stance this today that made sense to me. He is using it as a way to manipulate the "base" (i.e. uneducated religious gun nuts) into getting to the poles this fall. The GOP has been losing these people recently, as they finally seem to be aware that they're insignificant to the Party. As such, making the election about the Supreme Court might be a way for McConnell to hold the Senate, which he's in danger of losing. Makes sense.