* In a highly symbolic move, ex-Assemblyman Adam Clayton Powell IV will endorse Manhattan Rep. Charlie Rangel today, according to a source with knowledge of the endorsement and confirmed by a campaign press release. A spokesman for Rangel, Bob Liff, said he had heard that the endorsement was taking place, but did not have direct knowledge of it. Ive also heard the same thing, and its always nice to be with Mr. Powell, Liff said. The endorsement will occur in front of a statue in Harlem of former Congressman Adam Clayton Powell, Jr., whom Rangel unseated in a primary in 1970. Now, Rangel faces perhaps his toughest test since then, running in a highly competitive five-way Democratic primary, which includes a top-tier challenger in state Sen. Adriano Espaillat. Powell IV, the ex-assemblyman, is the son of the former congressman. In 2010, Powell ran against Rangel but lost by a substantial amount, despite scandals swirling around Rangel at the time. But now, the redistricting process has made the seat far more Latino-heavy, and Rangel faces a tough test from Espaillat and three others.