Six-term Illinois Congressman Tim Johnson says he will not run for re-election.  The Republican represents the state's 15th District, which includes Champaign-Urbana and parts of Normal and Bloomington.  Johnson reportedly was facing difficult prospects for re-election after his district was redrawn.  The announcement leaves the GOP searching for a possible successor.  In a statement today, Johnson said he will serve out the remainder of his term, which expires in January, but will not stand for reelection in November.  He called his district's redrawn boundaries "grossly gerrymandered."  He said he'd like to return to practicing law and spend more time with his family.