When the Congressional Black Caucus wanted to pay off the mortgage on its foundation’s stately 1930s redbrick headquarters on Embassy Row, it turned to a familiar roster of friends: corporate backers like Wal-Mart, AT&T, General Motors, Coca-Cola and Altria, the nation’s largest tobacco company. Soon enough, in 2008, a jazz band was playing at what amounted to a mortgage-burning party for the $4 million town house... From 2004 to 2008, the Congressional Black Caucus’s political and charitable wings took in at least $55 million in corporate and union contributions, according to an analysis by The New York Times, an impressive...