@Han: Of course I agree with closing/capping loopholes and deductions, it's a great idea that should be a major piece of any serious tax reform. However, a 35% top rate is already insanely low (it's one of the lowest among developed countries) and bringing it down further at the moment when we're talking about budget austerity, as Romney pledged, is absurd. There's also the fact that Romney's plan has been proven to be unworkable by several independent studies (at least, unworkable without taking a certain number of highly unpopular and economically detrimental measures).
I meant the general principle of Romney's plan, which has been endorsed at least once by the Economist (not Romney's specific plan, but the broad idea of lowering rates and simplifying the tax code; even the Simpson-Bowles commission supported this idea). It's probably true that Romney wouldn't have been willing to go far enough in eliminating loopholes and deductions to make his tax plan work (assuming that we're not taking into account job growth that would hopefully arise from tax reform), but that doesn't meant that the idea is wrong in principle.
Also, we accept the Keynesian argument that government intervention is necessary during a recession to stimulate aggregate demand, why would raising taxes on anybody be a good idea? There's an argument to be made that the harms would be outweighed by the gains and that we have no other choice but to raise taxes on the rich because of our deficit, but that doesn't mean that raising taxes on the rich is positive for the economy in and of itself (and for example, ending the Bush tax cuts on the rich wouldn't only force them to pay "a little more":
http://www.politifact.com/truth-o-meter/article/2012/aug/07/would-millionaires-pay-little-more-taxes-under-oba/). The fact that Obama and the Democrats want to extend the Bush tax cuts for the poor and middle class implies that they do indeed buy the argument that lower taxes are better. As Charles Krauthammer said, if the Clinton tax rates were so great, why not just go back to such rates for everybody?