As the presidential campaign begins in earnest, both candidates are trying to define themselves and each other. But the distinctions are blurred. "Blue Dog" Congressional Democrats say Barack Obama's too liberal, while labor leaders worry that he's not liberal enough. John McCain is supposed to be a "maverick" Republican, but he's sounding more like President Bush. Is he or is he not a real conservative? Why are some Republicans calling themselves "Obamacons?" Will those labels still matter this coming November?