During the 2000 Republican primaries, Karl Rove launched some viciously personal ads against John McCain. While the fight was dirty on both sides, many felt the Rove ads helped tip the scales in favor of G.W. Bush.
McCain himself felt such. He later stated that "there is a special place in hell for people like Karl Rove."

So who is directly McCain's current smear campaign against Obama? The same Karl Rove.
I suppose the shit doesn't fall far from the GOP tree.