The Bush Tax Cuts contained demand-side cuts to rates (2001), and supply-side cuts to investment taxes (2003). Romney wants to keep current rates, but cut investment taxes for the middle class (who unfortunately don’t have enough money to invest to make a difference in the economy).
If Romney is the nominee, then what is this battle over tax rates about? Not much. Romney already gives away the game by allowing that the rich should pay more investment taxes than the middle class. At that point Obama can come back with rates, the deficit and other stuff which muddles and confuses the issue.