What is the optimal upper marginal tax rate? Should it be much higher than it is now as it was in previous more prosperous and more egalitarian times? Or if you do raise rates in that way will you stop innovation and see all the job creators "going Galt"? Krugman discusses an interesting study by Peter Diamond and Emmanuel Saez here. This study evaluates the effect of high taxes as a disincentive so as to arrive at an optimal rate. The result? 70%. Much like it was back in more prosperous times. Maybe the study is wrong, but it's important for people on the right to remember that just because it sounds plausible that higher taxes do more harm than good that doesn't necessarily make it true. The data and facts matter.
Also a couple of links from Bruce Bartlett. In the first he talks about how Republican solutions to our economic problems are precisely the opposite of what CBO and other data indicate would work. In the second he talks about how the tax hikes of 1990 and 1993 clearly were causal in deficit reduction and they were of course likewise opposed by most Republicans. There are workable solutions to our current fiscal problems. Republicans just won't allow them.