John Sides argues HERE that the mood of the American public “tends to react against prevailing government policies…[A]fter the government does more and spends more, policy mood becomes less liberal; after the government does less and spends less, it becomes more liberal”:
In particular, the public’s policy mood responds to changes in party control of the White House. The public becomes more liberal during the administration of Republican presidents, and more conservative under the administration of Democratic presidents.
This was certainly true from January 20, 1969 to August 9, 1974, although it is hard to argue the nation got more conservative before that under LBJ and JFK.