Paul Krugman has become to print media what Keith Olbermann is to television: a Left-leaning prince of darkness. A professor of economics and international affairs at Princeton this decade, Krugman, now 56, has cultivated a recognizably caustic style of scoring points against free-market economics in theory and practice, especially in his New York Times op-ed and blog columns. The problem is that as he’s become a public figure, he’s shed, or at least has kept well-hidden, his empirical sense.