Congressman Mel Reynolds, the Rhodes scholar whose political rise created a wave of optimism in Chicago's black communities, may spend the rest of the decade in jail. "You threw it away," Judge Fred Suria told the two-term Democrat today after sentencing him to five years for having sex with an underage campaign worker and for soliciting child pornography. Reynolds had just completed a 40-minute courtroom rant in which he blamed racism and the media for his downfall. Replied Suria: "This case is not about race. This case is not about politics."