Let me say a bit about the introduction. This is where Krugman explains his current understanding of how things got much worse than anyone, himself included, thought they could just three years ago. (Like everyone else, he's being radicalized by Bush.) Thus: we are now governed by a reactionary party with a radical (he says "revolutionary") agenda, basically that of undoing the legacy, domestic and foreign, of FDR. They even say this, but people, especially the punditocracy, discount it, because they don't realize that, like any "revolutionary power," the GOP really means it, and is not going to be bought off with the usual compromises. Joshua Marshall and Nicholas Confessore have recently argued for similar theses. I wish I found them less convincing than I do.
Something Krugman doesn't emphasize enough, here, is a tactical point. Suppose you are a leader of a political party with a radical agenda which is actually quite unpopular (as Krugman notes, many voters refuse to believe that anyone could be serious about some of it), hasn't won a national majority in more than a dozen years, and has the demographic tides running against it. Through a combination of parliamentary flukes and lying about your program, you come to power. What, exactly, is your incentive to not ram as much of your agenda through as you possibly can? Normally parties don't fight everything to the hilt, because of the "shadow of the future", the sense that they'll need to cooperate with other parties and anyway there'll be another chance. But a party in that position, no possible future casts a moderating shadow --- this is its last chance, unless it is able to smash the existing order and build a new one entrenching its power. (People used to discuss this in connection with Communist parties under the catch-phrase "one man, one vote, one time".) Hence maximalism.
If, after finishing the introductory textbook he's working on now, Krugman is looking around for a new research topic, I would suggest that he consider political economy, and more especially the economic basis of ideology. His excellent essay on the growth of economic inequality in America (sadly omitted from The Great Unraveling), which is the material basis (as we used to say) of the movement, would be a good place to start.
Economics / North America / Politics
Currently in print as a hardback, ISBN 0-393-05850-6 [buy from Amazon]