Three canyons cut through the political landscape between National and Labour.
One is in the workplace. Labour sees wages and conditions (including safety) as the sustenance of workers and their families. National sees them as a cost to business.
The second is in foreign policy. For 65 years Labour has leaned more to multilateral processes and resorted to alliances as temporary second bests. National has always put more faith in alliances and has at times been deeply sceptical of the United Nations. Iraq sharply delineated that ideological ravine.