This will be saved for the debates. When Obama talks about "Change" McCain can simply pooint out that he was calling for "Change" when Obama was calling for donations from Freddie Mac.
McCain can lay the financial crisis right at Obama's feet and all he can do is step in it.
You can’t hold back and wait. The opinions on these issues are being formed NOW. By the time to debate comes around, the conventional knowledge will already have been cemented and McCain will have too little time to explain it.