Kentucky residents are used to close, competitive races that could be decided by a nose -- just not the presidential kind.  Home to the Kentucky Derby, the most famous US horse race, the state has not voted in a contested primary for the White House in decades. So it has been uncharted territory for residents ever since Democratic presidential candidates Hillary Rodham Clinton and Barack Obama began dropping by to make their pitches before the state's May 20 primary. "Kentucky always picks the president," Clinton said last week in Louisville. And "for too long we have let places like Kentucky slip out of the Democratic column."