Cassidy on Keynes and Reagan

Econ 302 midterm question 2(a):

The fiscal policies enacted by the Reagan administration included significant cuts in taxes and increases in (military) spending. Illustrate the effects of this fiscal policy using an IS-LM diagram. 

While my students were asked to work out the results in (Keynesian) theory, the data are consistent with its prediction:

The red line (right-hand scale) is GDP growth, which is negative in 1982, but strongly positive in 1983 and 84 ('Morning in America'), and the blue line is the federal deficit as a percentage of potential GDP, which shows the effect of Reagan's fiscal policy.

Apropos of this, John Cassidy has a nice post arguing that Reagan was a closet Keynesian:

In strict terms, Reagan’s neglect of the deficit wasn’t Keynesian. Keynes himself believed in letting the deficit rise in a recession and paying down debts in the good times. In America, though, Keynesianism has always been associated with stimulus programs, big government, and deprioritizing the deficit. In all of these ways, Reagan was a Keynesian. But a word to the wise: don’t waste your time trying to tell that to anybody in the Republican Party.