The most recent winner of the Nobel economics prize says Donald Trump is unlikely to be a good U.S. president and argues that the billionaire’s popularity is just one manifestation of how growing income inequality can warp the political landscape.

“I don’t think it would be a great idea if Donald Trump became the president of the United States,” Angus Deaton said in an interview on Monday, following a press conference in Stockholm, where he’s officially being awarded his Nobel this week. 

The 70-year-old Princeton University professor, who received the Nobel for his analysis of consumption, poverty and welfare, says the popularity of Trump and others far removed from the political mainstream reflects voter disillusionment with an establishment that has presided over a dangerous increase in income inequality across the globe.

Especially in an environment of sluggish economic expansion, the growing divide between rich and poor is “really terrible,” Deaton said. “In growing economies, I can get something and you can get something, whereas in a stationary economy, if I get something extra, you’re going to get something less; I think that helps explain a lot of the bitterness in American politics today.”

Trump is leading the group of Republican contenders vying to become the party’s candidate in next year’s presidential election. A Nov. 27-Dec. 1 CNN poll had him at 36 percent, followed by Ben Carson at 14 percent. All major polls put Trump in first place in the Republican field, with margins greater than 20 points in some cases.

“If people with enormous amounts of money use that to buy politics, for instance, or if the growing inequality means that there is a very angry minority that’s left behind and that votes for people like Trump, or for fascist parties or whoever, then I think that really is a threat to the future,” Deaton said. “So those are ways in which growing inequality, in a very broad sense, can threaten the prosperity of everyone.”

In Europe, the threat is particularly acute as the refugee crisis stretches the region’s resources to breaking point. The risks are even greater than during the debt crisis, from which Europe has only just emerged. “The migrant crisis could certainly make the economic situation very much worse,” the laureate said.

The situation has led to the political rise of “crazy people on the fringes,” Deaton said. But the fallout in the U.S. has been “much worse because there is almost no threat, and yet these politicians are being demagogues about it.”

Deaton’s research has focused on health in both rich and poor countries, as well as on measuring poverty in India and around the world. Born in Scotland, and a citizen of both the U.S. and the U.K., Deaton obtained his Ph.D. from the University of Cambridge. His 2013 book, “The Great Escape,” maps the origins of inequality and its fallout spanning 250 years of economic history.

Growing inequality is “an enormous threat,” he said. But not everything that creates a bigger income divide is bad. “It’s complicated,” and it’s not fair to conclude that inequality per definition is bad for economic growth, Deaton said. Rather, slowing growth exacerbates income inequality.