NEW YORK (Billboard) - Today's hip-hop constituency possesses even greater media access and financial clout than when Public Enemy first exhorted the hip-hop generation to "Fight the Power" in 1989. Rap artists have since tackled gang violence, South African apartheid, drugs, police abuse and more. Now they want to play an instrumental role in this year's presidential election. Political groups are tapping hip-hop to engage not just young people but all disenfranchised people of color, hoping their votes will unseat President Bush. "Most hip-hop followers come from struggle. There's a common agenda for all of those who are locked out,"...