Incoming national economic council director Larry Kudlow took aim at The New York Times’ columnist and Nobel Prize winning economist Paul Krugman, in a Friday tweet.

Krugman fired the first shot in his column saying that the job of NEC director “requires a good enough understanding of economics to recognize good and bad advice, but it also requires other skills, managerial and diplomatic; basically, the council’s director has to be an honest and effective broker of other people’s ideas and actions.”

He continued in a swipe at Kudlow:

So when Trump chose Larry Kudlow to replace Gary Cohn in that role, Kudlow’s remarkable track record on the economy — he’s been wrong about everything — was only part of the problem. Beyond that, nothing in Kudlow’s role as a shouting head on cable TV has prepared him for the job he’s supposed to do. But no matter: According to Kudlow, the president says he looks “very handsome” on TV.

Kudlow responded in a barbed tweet saying: