The rise of Trumpism is a defining challenge for progressives. The left is used to debating the right on the traditional conservative triad of a strong military, social conservatism, and tax cuts. But Trumpism represents new and politically dangerous terrain. It taps into nationalism, the most powerful motivating force in modern political history. It offers a potent emotional appeal to communities that feel ignored. Whereas the center-left can seem managerial and technocratic, Trumpists speak to the heart. And they shouldn’t be underestimated. They outmaneuvered the left in both Britain and Finland. Trump claimed the Brexiters “put the United Kingdom first, and they took their country back,” adding, “we’re going to do the exact same thing on Election Day 2016 here in the United States of America.”

But the Trumpists also have weaknesses. They can win power—but they don’t know what to do with it. After the Brexit decision, the leaders of the Leave campaign seemed dazed and confused, and had no plan for what should happen next. The most famous Brexiter, the wild-haired Conservative MP Boris Johnson, had long wanted to be prime minister (a step toward his childhood aim of becoming “world king”). But when British Prime Minister David Cameron announced his resignation, Johnson’s campaign to replace him quickly fizzled out. Johnson was recently appointed foreign secretary and many people are extremely skeptical about his credentials—“a liar with his back to the wall” was the French foreign minister’s description of Boris.

Similarly, after the Finns Party entered the government in Helsinki, they hemorrhaged support, and polls suggest their backing is down to 10.7 percent. The Finnish populists found that governing is a lot harder than campaigning. Wrestling with complex issues like the Greek bailout and the struggling economy, and making inevitable compromises, the Finns Party couldn’t live up to their grand slogans and promises.

Similarly, if Trump wins, there’s a good chance that he will be all at sea. For one thing, he has no experience of managing Congress. Of course, by then it might be too late to stop his agenda.