A number of progressive reforms were introduced during Kampmann's time as Prime Minister.

Kampmann was one of the most intelligent and knowledgeable Danish Prime Ministers, though his conduct in office was erratic.

Through most of his adult life he suffered from bipolar disorder, and in his darker moments he tended towards alcoholism and frequently 'disappeared' from view for days at a time, leaving the government without its head.

Kampmann resigned on 3 September 1962 after a series of heart attacks, and was succeeded by Jens Otto Krag as leader of the Social Democrats and as Prime Minister.

In retirement he worked as a political commentator and head of the Press Complaints Commission.