By any standard, white voters’ rejection of Democrats in November’s elections was daunting and even historic. Fully 60 percent of whites nationwide backed Republican candidates for the House of Representatives; only 37 percent supported Democrats, according to the National Election Poll exit poll conducted by Edison Research. Not even in Republicans’ 1994 congressional landslide did they win that high a percentage of the white vote. Moreover, those results may understate the extent of the white flight from the Democratic Party, according to a National Journal analysis of previously unpublished exit-poll data provided by Edison Research. The new data show that...