Six days before the Ohio Republican primary that will either end or kick-start his presidential campaign, Ohio Gov. John Kasich was playing catch-up. He started a Wednesday swing through the Chicago suburbs at Navistar, a truck manufacturer, and recounted that the chief executive had just told him that “international bureaucrats” were taking advantage of trade deals.

“We’re not going to sit here and have the American worker beaten on because we’re relying on some international bureaucrat,” Kasich said at the factory and at a stop in Cook County. “Now, that doesn’t make the free-traders in my party happy. Tough. Because I am for free trade.”

Hours later, Donald Trump — who defeated Kasich in Michigan and is leading in Ohio polls — put the trade issue in his own terms.

“You know, Michigan’s been stripped,” Trump told CNN’s Anderson Cooper on Wednesday. “You look at those empty factories all over the place. And nobody hits that message better than me.”

As the primary season moves to the industrial Midwest, blunt talk about trade — and deep skepticism — are winning out over nuance. Trump’s victory in Michigan was expected, but the victory of Sen. Bernie Sanders of Vermont defied every poll and rattled a Democratic establishment that was already talking about a race between Trump and Hillary Clinton.

Bernie Sanders won Michigan on March 8 by getting votes from several key groups. (Peter Stevenson/The Washington Post)

The salience of trade, in a state where unemployment had tumbled more than half since the start of the Great Recession, blindsided a Democratic Party that has struggled to find coherence between its labor base and its neoliberal leadership. It also worried Republicans, whose leaders and donors are resolutely in favor of free trade.

“There has been a bipartisan conventional wisdom that the damage done to working-class jobs and incomes are simply part of inevitable changes, ones we cannot and should not challenge,” said Larry Mishel, president of the left-leaning Economic Policy Institute. “Even President Obama is blaming inequality problems on technological change, which is not even a plausible explanation for post-2000 America. People correctly understand that many elites simply believe that wage stagnation is something we cannot change.”

The post-2009 increase in overall employment has masked a steady decline of Midwestern manufacturing jobs. Ohio is down 6,900 manufacturing jobs from the start of 2008, according to the Labor Department, a decline of 9 percent. It has lost one-third of the factory jobs it had in 2000 — a total of 340,000.

Michigan has gained just 1,300 manufacturing jobs since the start of 2008, and it still has 285,000 fewer factory jobs than it did in 2000, a drop of 32 percent.

In Michigan, exit pollsters for the first time asked voters whether they thought trade created or took away American jobs. The “take away” faction made up 55 percent of the Republican primary vote and 57 percent of the Democratic primary vote. Trump won the GOP faction with 45 percent, and Sanders won the Democratic side with 56 percent.

Both men spent long sections of their stump speeches to assault trade deals and the political classes that had negotiated them. They differed only in the analysis of whether the dealmakers were venal or merely stupid.

“Many, many Republicans and far too many Democrats supported these disastrous trade policies,” Sanders said Sunday at the pre-primary debate in Flint. “Not only job loss by the millions, but a race to the bottom so that new jobs in manufacturing in some cases pay 50 percent less than they did 20 years ago. How stupid is that trade policy?”

In the 2008 Democratic primary, Barack Obama made a fitful promise to renegotiate the North American Free Trade Agreement, but it did not move votes in Ohio. This year was different, because the candidates were different. Lori Wallach, the director of Public Citizen’s Global Trade Watch, said this election has elevated a candidate in each political party with a long record of questioning trade deals. She recalled Trump speaking out along with Ross Perot against NAFTA in the early 1990s, and Sanders being one of the first members of Congress to actually read the agreement in full before it was voted on.

“On a bipartisan basis, the political class in this country has underestimated the political potency of the public’s opposition to job-killing trade agreements or have dismissed it as ill-informed,” she said. Trump and Sanders, she said, are “articulating, pretty concretely, why what’s happening has happened, and here’s how we do it differently.”

Stephen Moore, a conservative economist who has advised several Republican candidates on economic policy this cycle and who supports free trade, said Republicans shouldn’t be surprised that voters have turned against trade deals.

“It’s really hard and painful to find something else to do when you’re 58 years old” and laid off, he said. “Our side has to do a really better job of explaining the ways trade makes people better off.”

No one on the mainstream right has really done so. The Club for Growth, a free-market group that has poured millions of dollars into anti-Trump TV ads, has focused on the mogul-turned-candidate’s past support for Democrats and his comfort with eminent domain law.

“What’s needed now by the supporters of free trade is a public education campaign to talk to these voters and explain to them and their family members what’s at stake,” said David McIntosh, the president of the Club for Growth. “It’s a matter of having an economic policy that will create new jobs to replace those jobs being lost. There’s a lot at stake here if we get into a trade war.”

Yet McIntosh was not shocked by the anti-free-trade sentiment rising in the primaries. When NAFTA came up for a vote, he, like Kasich, supported it — and had to fight a backlash at home.

Pat Buchanan, the insurgent Republican who won the New Hampshire primary in 1996, was one candidate who capi­tal­ized on the backlash to both NAFTA and the General Agreement on Tariffs and Trade (GATT). At the time, a stronger Republican establishment managed to stop him. That experience made Buchanan wonder why the elites in both parties seemed so startled by Michigan.

“If they’re surprised, there’s something wrong with their antennae and their radars,” Buchanan said Wednesday. “When we were arguing against NAFTA and GATT, it was quite clear that the country was with us. Global free trade has never had, in my estimation, real majority support. In Michigan and Ohio, you’ve got voters who have lived through what we predicted.”

DePillis reported from Washington. Jim Tankersley in Washington contributed to this report.