The pilot indicated that during the landing, through the flare and main landing gear touchdown, all flight parameters were normal. He stated that after the nose wheel touched the ground, the airplane "veered" to the right. The pilot reported he applied full left rudder and aileron but the airplane departed the right side of the runway into a ditch. Examination of the airplane revealed substantial damage to the fuselage and engine firewall. Continuity of the rudder and nose wheel cables was verified to be correctly rigged and serviceable. The approach and landing were oriented on runway heading of 070 degrees and reported wind was from 080 degrees at 7 knots. The pilot reported no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.