Warren and Sanders can’t easily follow Scholten’s advice. While both senators have criticized the way Trump has implemented his trade policies, they’ve supported trade barriers in general. In outlining her trade policy last month, Warren declared that “tariffs are an important tool.” In March of last year, she called them “one part of reworking our trade policy overall.” When Trump imposed tariffs on foreign steel and aluminum last June, Sanders said, “I strongly support imposing stiff penalties on countries like China, Russia, South Korea and Vietnam to prevent them from illegally dumping.” While Harris hasn’t praised tariffs, she’s come out against NAFTA and TPP.

Read: The progressive nonargument against Biden

With a deeply unpopular trade war tanking the economy, these views are now a political liability, especially in Iowa. By attacking not merely Trump’s implementation of tariffs but the very notion that tariffs benefit America, Biden could link himself to Barack Obama and link his progressive challengers to Trump. Instead of backing off his long record as a free trader—as Hillary Clinton did when she flip-flopped on the TPP in 2016—he could argue that America’s mounting economic woes are proving him right.

They are. Trump’s tariffs have not revived American manufacturing. To the contrary, according to Mark Zandi, chief economist at Moody’s Analytics, they’ve already cost the United States 300,000 jobs. And they’re based on a series of wildly exaggerated claims about the way China “cheats” on trade. In fact, as I’ve argued previously, China imposes a lower trade-weighted average tariff than Argentina, Brazil, India, South Korea, Indonesia, South Africa, Turkey, Russia, Saudi Arabia, and Mexico. According to the U.S. Chamber of Commerce, China does a better job of protecting the intellectual property of foreign companies than Turkey, Brazil, South Africa, and the Philippines. Yes, trade with China hurts some American workers, but it benefits many others, and makes America wealthier overall. The problem is that America, with its meager social safety net and low taxes for corporations and the ultra-rich, doesn’t adequately redistribute that wealth to the Americans who need it most.

Making this argument might hurt Biden with certain protectionist labor unions. But those unions are out of step with Democratic voters. And defending free trade would fit into the larger argument behind Biden’s campaign: that he’s more in touch with rank-and-file Democrats than are the progressives who criticize him on Twitter. Left-leaning activists may oppose Obama’s trade policies, but ordinary Democrats support them. And while Democrats are haunted by Trump’s victories in the industrial Midwest, his protectionism isn’t even popular there. In May, The Washington Post’s Greg Sargent noted that, according to polling from Quinnipiac, voters in Pennsylvania, Michigan, Wisconsin, Ohio, and Iowa disapproved of Trump’s trade policies by an average of 15 points.

It’s an odd feature of our political discourse. Although frequently labeled “populist,” Trump’s trade policies aren’t popular. Recognizing that could help Biden win Iowa and perhaps the nomination itself.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.