Mark Steyn explains.

For a century and a half, race is one issue the Republicans have been right on-- or, at the very minimum, less wrong. We've grown used to the Democrats' strange black-is-white world, where Al Gore apparently genuinely believes his father was a civil rights crusader rather than a civil rights obstacle. Segregation is the Democrats' history, and for Trent Lott to give them an excuse to dump it on the GOP doorstep is all the reason Republicans needed to be done with him once and for all.