This election cycle keeps demolishing expectations on both sides of the aisle. In Tuesday’s contests, Donald Trump defied analysts who predicted a decline in his support after the Republican field narrowed and Trump finally came under heavy fire from negative ads and debate attacks.

Those predictions turned out to be as accurate as earlier ones that shrugged off Trump as a flash-in-the-pan, a momentary vicarious release of populist anger. Trump easily won primaries in Michigan and Mississippi, as well as the GOP caucuses in Hawaii. Marco Rubio, who led the negative attacks on Trump, was shut out of the delegate allocation in all four contests.

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Democrats offered a big surprise of their own on Tuesday. Hillary Clinton expected to roll over Bernie Sanders in Tuesday’s two Democratic contests after losing both Maine and Nebraska to the progressive upstart over the weekend. Clinton won Mississippi easily as expected, but Michigan refused to play to the script. She had a commanding polling lead in the key Rust Belt state; not one poll listed by Real Clear Politics for the entire 2016 cycle put Sanders on top, and only one taken in September put her lead at less than double digits. The polling average over the last month had Clinton ahead by 21 points in the primary state. And yet Sanders pulled off a stunning upset, edging Clinton 49.8/48.3 in the popular vote.

What happened? Clinton had hardly neglected Michigan. She made the water crisis in Flint a particular focus of her attention, sending daughter Chelsea to head up relief efforts in the beleaguered city. At the same time, Clinton dropped what she must have expected to be a devastating blow on Sanders – his vote against the automaker bailouts during the financial crisis. In Michigan, where the automobile industry has dominated state politics for decades, that attack could easily have been considered fatal to even the thin hope Sanders had of gaining delegates in the proportional-allocation primary.

Sanders fought back nonetheless. He rebuked the attack as a cheap shot, noting that he had voted for a stand-alone automaker bailout package earlier. His objection, Sanders explained, was in rolling the automaker assistance into the Troubled Asset Relief Program (TARP), which bailed out Wall Street with inadequate government oversight. Hillary Clinton, Sanders pointed out, supported the Wall Street bailout package.

Related: How Sanders Defied the Odds to Beat Clinton in Michigan

That may have had a significant role in yesterday’s upset. Esquire’s Charles Pierce spent a few days in Flint and discovered the depth of Clinton’s miscalculation. Calling it “one of the more interesting examples of unintended consequences that I'd heard in a while,” Pierce reported that Flint voters found Clinton’s attack offensive and cynical.

Exit polls showed that the problems ran deeper than just the question of bailouts. Clinton’s accusation opened her up not just on the bailout issue but also on her support for free trade agreements that autoworkers believe left them unfairly vulnerable to foreign competitors. The Detroit Free Press quotes pollster Bernie Porn as saying that Clinton’s connections to Wall Street corporations and her support for free-trade deals – such as the Trans-Pacific Partnership (TPP) Barack Obama wants Congress to sign – caused the political earthquake in Michigan. "The trade issue was a late-breaking issue that not only affected the whole discourse of the campaign,” Porn said. “I think it turned a lot of voters away from Hillary Clinton.”

This corresponds with the remarks made by an exultant Trump after being declared the Republican primary winner in Michigan, touching on a major theme of his campaign since it launched nearly a year ago – trade. During his rambling, stream-of-consciousness remarks after the win, Trump repeatedly emphasized that our trading partners and allies take advantage of the American worker, and blamed it on the “babies” doing the negotiations for the US. “They have no fear of our government,” Trump declared. “They’re dealing with babies. … They are grandmaster players and we have people that shouldn’t be negotiating for us.”

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This gets to the heart of the populist moment in the US. It goes beyond disappointment and frustration with the political institutions of our country, although it certainly includes that. Voters are not turning to Trump and Sanders only because Congress’ job approval ratings remain mired in single digits. The problem is less that of a failed system than of a rigged system, where corporations have pushed a free-trade agenda that has stalled American wage growth, led to uncontrolled immigration, and two parties who have more interest in the status quo than in the welfare of ordinary Americans. That system has set the wolves on American workers, many voters feel, and left their fate in the hands of “babies,” or worse.

That appears to be true even in the Republican Party, which has long stood for open markets and free trade as a philosophical touchstone. Trump may not do quite as well in closed primaries as he does in those contests where non-Republicans can vote, but it’s clear that most of his support comes from Republican voters, a conclusion reached by The Washington Post’s Philip Bump as well. The GOP has always had a minority contingent preaching protectionism, but in this cycle, it may have become a plurality on its way to a majority.

It may seem ironic that Trump, of all people, has captured that impulse and helped transform it into a movement. As Marco Rubio and others have pointed out, most of Trump’s products are manufactured abroad – in China and Mexico particularly. However, Trump argues that he’s only living in the environment created by decades of failed American leadership, and that – in some sense – it takes a globalist to arrest globalization.

The lesson this week is that voters want not just a fight, but potentially a trade war. If they can’t get that from the so-called establishment, then they’ll look to outsider populists like Trump and Sanders—hoping they can deliver on their promises. We may have reached the limits of American engagement in globalized markets, and a new era of incremental protectionism, mandated by voters who are determined to overturn all of the apple carts. Free-market conservatives may find themselves searching in vain for a chair when the music stops in a Trump-led GOP.