Barack Obama's new ad hits cable news today, and he's making a critical mistake in attacking McCain. Obama's numbers are falling not because people are gravitating towards McCain, but because they don't know who Obama is and the McCain ads mocking him are resonating. In an effort to be all things to all people, Obama has left voters confused and uncertain as to who he is. Defining himself, not attacking McCain, should be his priority. To give just one example about how Obama's campaign is playing fast and loose with his bio, consider that a Spanish language ad says that Obama's father was an immigrant while a later one notes that Obama was raised by a single mother. These may not be mutually exclusive, but they do present a somewhat contradictory narrative. Obama's priority should be giving voters some clear picture of who he is. If he doesn't, it's not going to matter if they believe McCain is running for Bush's third term.