We are all Keynesians now (including Ronald Reagan)
The New York Times has a surprisingly fun interactive feature on the American government's responses to various recessions, narrated by various economists. The highlight is Jeff Frankel of Harvard's argument that the '81-'82 recession was eased by Ronald Reagan's expansionary fiscal policies, which Frankel calls "Keynesian in consequence, if not in design":
Even though it wasn't done under a Keynesian banner or with Keynesian intention, it did have Keynesian effects, and it did help pull us out of the recession of 1981-82.