With just three primaries left in the race for the Democratic presidential nomination, an analysis of results in the 33 primary states for which there are exit polls reveals the decisive role identity politics played in cleaving the party and determining the likely outcome: Barack Obama's overwhelming margin with black voters trumped Hillary Clinton's broad backing from white women. The finding suggests that, despite recent attention to Obama's perceived weakness with a segment of white voters because of race, his immediate challenge is to assuage the letdown and even bitterness of some white women who, along with African-Americans, have been...