Noah Smith writes better than I can and in particular that

Nobel-winning economist Paul Krugman recently claimed that John Maynard Keynes — or the general idea of Keynesianism — is winning the battle of opinion in the public sphere. George Mason University economist and blogger Tyler Cowen responded, playing devil's advocate, and listed a bunch of points that he thinks indicate that Keynesian ideas (liquidity traps are important, austerity during recessions is destructive, fiscal stimulus is useful) might be losing the substantive battle.

Econ blog arguments are fun, so I'll play devil's advocate squared — angel's advocate? — and go through some of Cowen's points.

Sure sounds like fun. Also Tyler Cowan is on my very short list of reasonable and reasonably honest conservatives (in fact, as not very far as my memory serves me, it is entirely possible that “Tyler Cowan” *is* my list of reasonable and reasonably honest conservatives).

Acting as devil^2 advocate, Smith concedes two points to Cowan

Here is Cowen:

Keynesians predicted disaster following the American fiscal sequester, and the pace of the recovery accelerated.

This is intriguing especially in light of the fact that everyone blames a 3 percent sales-tax hike in April for crashing the Japanese economy. If that small tax increase sent the Japanese economy into a tailspin, why didn't the across-the-board spending cuts of the sequester inflict similar damage on the U.S. economy This does make me doubt the standard Keynesian story.

I wonder which Keynesians predicted disaster. I certainly didn't and I don't recall Paul Krugman doing so. I thought the policy was obviously bad and the opposite of what should be done, but I certainly didn't expect it to cause a recession. Here (and elsewhere) Cowan appears to use constant growth as a baseline. But the recovery has consistently disappointed (except for the “morning in America” surpassingly rapid turnaround when ARRA spending started).