Much like Milton Friedman Krugman has found a voice in the political pundit area. At least Krugman comes from a more realistic economic theory base as a New Keynesian than Friedman did as a neoclassical economists pining for the unrealistic and never before seen free market. The advantage that a Keynesian has over other schools of economics is that Keynes concentrated on understanding the economy that we have. Other schools like the neoclassical economics school concentrate on changing the current economic system to match an unrealistic ideal economy that doesn't exist and can never exist.
The problem with the New Keynesians like Krugman is that they have met the neoclassical economists more than half of the way between the realism of Keynes and the fantasy of the free market enthusiasts. Krugman readily admits that he catered to and bent his research toward the neoclassical economists' philosophy in his research so that he could be published in their journals. Certainly he wouldn't have won the Nobel prize in economists had he challenged the neoclassicists more openly.
A prominent neoclassical economist at Harvard, Greg Mankiw routinely writes abstracts and conclusions that follow the neoclassical dogmas but in the body of the paper he presents the actual evidence that he found that routinely deny the dogmas. He knows that most people read only the abstract and maybe the conclusion and don't read the main body of the paper. He has done this for years.
The neoclassical economic is the economics of Marshall that was shown to be in error almost from the very beginning. In fact, Keynes started out to write a defense of his mentor Marshall and his theories. But it didn't take Keynes very far into the research for what became his General Theory to realize that Marshall's neoclassical theories didn't explain the industrial economy that we had in 1936. Keynes realized that the industrial revolution had changed the economy to one dramatically different from the economy of the classical economists, that is of Smith, Ricardo, Malthus, Marx, etc. and that the further development of their theories by the neoclassical economists like Marshall didn't come close to explaining the economy of 1936. And that the single largest difference was that the 1936 economy was no longer supply driven, that is determined by the amount of capital and investments, but was becoming more and more led by demand. That supply, that is capital, was no longer land like it had been in the mainly agricultural economy of the classical economists but now was only money. And money in the modern fiat money system is not a limited resource. Keynes barely could see what we now know is true, that the economy produces the amount of money that it needs in a fiat money system. That what is limiting the economy isn't the money available to invest but the money in the hands of the consumers to buy goods and services.
This revelation of Keynes and the subsequent work done by Keynesians through the decades since have been proven time and time again. But these revelations didn't sit very well with a small but powerful group of people, rich investors who didn't like to be told that they weren't very important to the economy any longer. The wealthy fund the schools that economists work and teach in. The wealthy hire the graduates of the economics schools. They could and they did impose their own views on the schools and on the economists. What was cobbled together was the monster of the neoclassical synthesis, a combination of the discredited neoclassical economics with as little of the much hated demand driven, investor belittling but realistic Keynesian economics as they felt that they couldn't ignore.
Over the years Keynes has been turned into a four letter swear word. Neoclassical economics went over into never Neverland of pure fantasy with supply side economics, the economics that to this day defines the economic policies that we follow. But you can't escape Keynes and his followers. They have explained and predicted every twist and turn, every fault of the supply side economic policies of today, including the Great Recession of 2008. The only economists who not only predicted the financial crisis that caused the recession but who also explained the timing and the reasons for the financial crisis, were the Post Keynesians.
