A Democratic superdelegate from New Jersey said this week he is worried that unifying the party behind Barack Obama may be difficult because the Clinton camp "has engaged in some very divisive tactics and rhetoric it should not have." Rep. Rob Andrews, who supported Hillary Clinton throughout the primary season, disclosed that he received a phone call shortly before the April 22 Pennsylvania primary from a top member of Clinton's organization and that the caller explicitly discussed a strategy of winning over Jewish voters by exploiting tensions between Jews and African-Americans.  "There have been signals coming out of the Clinton campaign that have racial overtones that indeed disturb me," Andrews said at his campaign headquarters in Cherry Hill Tuesday night after he lost his bid for the U.S. Senate nomination. "Frankly, I had a private conversation with a high-ranking person in the campaign . . . that used a racial line of argument that I found very disconcerting. It was extremely disconcerting given the rank of this person. It was very disturbing." Andrews said the phone call came after he angered the Clinton camp by making some positive comments about Obama. He would not disclose the caller's name because of the private nature of the conversation.