Before the Bush years, Paul Krugman was simply an economist. As a young academic, he made a tremendous splash through his work on economic geography, developing what came to be known as New Trade Theory. I’m not an economist, but luckily the internet is full of them and Ed Glaeser (along with a few others) has a good explanation of what Krugman’s contributions were. At the most basic level, Krugman’s trade work investigated something that had long gone under-analyzed in economics. Under standard Ricardian trade theory, countries have natural endowments–good soil for grapes, a countryside full of sheep–that give them a comparative advantage. Trade between two countries creates a net welfare gain because each country specializes in their comparative advantage and then trades with the other. In the iconic example used by Ricardo of England producing wool and Portugal producing wine, the respective comparative advantages are fairly clear and straightforward. But in an industrial age, just what determines what a country’s comparative advantage is an open question. And it’s one that Krugman’s work attempts to answer.

Of course, Krugman is now best known as a New York Times columnist, public intellectual, and most importantly an outspoken liberal. It wasn’t always so. Krugman’s politics, as even he will tell you, were generally centrist in inclination for much for his adult career. (He even had a low-level job as an economic advisor inside the -gasp-Reagan administration) But to his eternal credit, he sniffed out the fundamental mendacity of the Bush administration long before it became fashionable and was honest, direct and relentless in criticizing what is now roundly and unanimously considered one of the worst administrations in American history.

And while he now proudly and eloquently declares himself a liberal, Krugman’s politics remain firmly a part of the mainstream, pragmatic center left. Which is why it’s so hilarious and bizarre to see him attacked from the Right as some kind of anticapitalist, radical.

Krugman’s own ideological and professional journey demonstrate two important truths about the ideological twists and turns of the last eight years. One, that the Bush administration has been so ideologically aggressive, so slavishly reactionary, they’ve managed to leave all but the most committed fellow travelers behind. And two, that combination of zealotry and malfeasance has been radicalizing for many figures who used to consider themselves placid centrists. In light of the destruction that modern conservatism has wrought, Krugman has recognized the importance for progressives to embrace mobilization, organizing and power, an insight too many establishment figures were slow to grasp.

More than any other mainstream figure, it was Paul Krugman who recognized these developments as they were happening. He’s been a truly heroic voice. We offer him our sincerest congratulations.