Obama, who draws massive crowds wherever he goes, has largely avoided the issue of race during his campaign. But volunteers who go door-to-door and phone-bank workers say racism and hostility is commonplace, though largely unreported, The Washington Post reported Tuesday.

One caller to a Obama campaign headquarters in Pennsylvania reportedly said, "Hang that darky from a tree" and another Pittsburgh resident told a volunteer, "White people look out for white people, and black people look out for black people."

Obama offices in Indiana were vandalized with racial slogans and other offices received bomb threats.

Exit polling from previous nominating contests show Obama fails to generate support from white, working-class voters who didn't go to college but his strong national appeal speaks to what some say is a generational gap in the issue of race, The Post said.