As Bill Clinton stated at the Dem' Convention (as best I can recall) - "He is going to reduce rates on the wealthy and then remove deductions. Which deductions? Well, what I gather so far is his answer is, 'We aren't gonna tell you.'"
This is a campaign being run on the theme of, "Don't vote for my opponent. He is the devil." Romney offers virtually NO policy guidance except for some pretty serious hints at a return to GW Bush.
Analogy time: Look, I despise Kobe Bryant about as much as any current athlete. But if you come to me and say, "I think Chase Budinger is a better player than Kobe," I will expect you to at least provide SOME justification for your position that discusses how good Budinger is, not simply a statement that Kobe COULD have played better over the past couple years.