Chinese shipping containers are stored beside a US flag after they were unloaded at the Port of Los Angeles in Long Beach, California on May 14, 2019. Mark Ralston | AFP | Getty Images

The cacophonous opening of the 2020 presidential campaign has clarified one thing: free trade is now politically homeless. That's remarkable, since Americans plainly recognize the benefits of trade expansion in an era of global economic integration. In last month's NBC News/Wall Street Journal poll, 64% called free trade "good for America." But a self-styled "tariff man" Republican president and Democratic rivals promising their own versions of trade confrontation have turned away from it. That inverts the bipartisan support behind trade expansion deals from Ronald Reagan's presidency through Barack Obama's. "The new bipartisanship is opposition to free trade," says Richard Haass, who advised past Republican presidents and now runs the Council on Foreign Relations. "It will be extraordinarily hard to resurrect a consensus that could pass a trade bill."

Economic analysis shows that international commerce benefits most Americans even as it imposes concentrated costs on a smaller number in domestic industries most adversely affected. Yet trade deals have come to symbolize global forces shaking middle America through widening income inequality and demographic change. Never mind that globalization would have occurred without them, or that automation erodes manufacturing employment more – the unpopular government officials and business leaders involved in trade deals provide irresistible targets. And the first chapter of the 2020 contest suggests that won't change soon. As he seeks reelection, President Donald Trump pursues a tariff war rattling financial markets and executive suites. On trade and immigration, a modern GOP dependent on working-class white voters embraces populism over business-friendly free-market conservatism. Democrats attract swelling numbers of affluent, college-educated voters thriving in the global economy. Flipping an earlier generation's pattern, the party's rank-and-file now embraces free trade more fervently than Republicans do. But that hasn't generated support for trade expansion among presidential candidates. Upscale Democrats tend to rally behind the party's tolerance on social issues, while traditional allies in organized labor target trade agreements such as the Trans-Pacific Partnership that President Barack Obama negotiated and that Trump scuttled. "It's tough to break from the sense of history," says Mark Muro, a Brookings Institution scholar who has documented the new economic profile of Democratic constituencies. Thus 2020 Democrats rip Trump for a clumsy and haphazard approach without rejecting trade confrontation itself.