Democratic Sen. Tim Johnson of South Dakota is in a Washington hospital. Johnson was taken there from the Capitol Wednesday afternoon after what aides believed might have been a stroke.
Johnson suffered from bleeding in the brain caused by a congenital malformation, the U.S. Capitol physician said, describing the surgery as successful. The condition, present at birth, causes tangled blood vessels.
Democrats hold a fragile 51-49 margin in the new Senate that convenes Jan. 4. If Johnson leaves the Senate, the Republican governor of South Dakota could appoint a Republican — keeping the Senate in GOP hands with Vice President Dick Cheney's tie-breaking power.