Yglesias observes:

Romney has quietly managed to skate through this whole campaign while hewing to a much more moderate line on taxes than his rivals. Now moderation is a relative concept. Romney wants to extend all the current Bush tax cuts, which on its own terms implies major long-term cutbacks to federal retirement programs, and would add to that a pretty expensive proposal to eliminate capital gains taxes for everyone earning less than $200,000. But there's tons of daylight between Romney and Perry/Gingrich on this front. Under the circumstances it's strange that the candidates have spent much more time engaged in hair-splitting disagreements about immigration than they have on taxes.