We've been down this road before, Obama must not think he can win where others have failed.
There has been a lot of talk about how Obama must not sully his "brand" by taking on John McCain and the Republican Party with pointed attacks. Following this argument, Obama is the candidate of bi-partisan change and conciliation and must not now appear too partisan. Further they say, Obama is too "black" to be so aggressive, he will appear to be an angry black male to his white audience.
I think this is mostly nonsense. The biggest mistake Obama can make is to appear above the fray in the coming months. This approach would play right into the hands of the Republicans who will depict it as being ivory towered and effete. "He's too sissy to stand up to John McCain" will go the background refrain. Like it or not, this kind of garbage has been working for the Republicans since Nixon, and there is no evidence the public has seen through it yet.
So what must Obama do? He must attack McCain repeatedly pointing out the dangers of McCain's foolish blustering, how his belligerent foreign policy team will lead us down the road to more war, not less. He must point out clearly the bi-polar direction of the American economy in the last 20 years and how we must change direction before it too late. While doing this he can deflect concerns about his image, occasionally using sarcasm, humor and satire. He did this well during the primaries with comments like "McCain is running for GB's third term"
This campaign runs a great risk of appearing too passive. That has been the undoing of several Democratic candidates in my life and it simply makes no sense to risk it again.