Senator Bernie Sanders at a rally in Dearborn, Michigan, on March 7th. Sanders unexpectedly beat Hillary Clinton in the Michigan Democratic primary. Photograph by Sean Proctor / Bloomberg via Getty Images

In an election year that has already shattered many received wisdoms, add another one to the scrap heap: the idea that the Democratic and Republican Party establishments were finally getting a handle on the popular insurgencies that have shaken up their parties.

In a result that FiveThirtyEight’s Nate Silver said before the race was called would count as one of the biggest upsets in polling history, Bernie Sanders defeated Hillary Clinton in Michigan, a key industrial state that has long been regarded as a bellwether for the entire Rust Belt. Making an unscheduled late-night media appearance before his victory had been confirmed, Sanders hailed what had happened as a repudiation to the pollsters and “the pundits who said that Bernie Sanders was not going anywhere.” He added that his campaign expected to do well in the West, where there haven’t been many Democratic votes yet. “This has been a fantastic night in Michigan,” he concluded. “We look forward to going to Illinois, Ohio, Missouri, and the other states that we will be competing in next week.”

Meanwhile, Donald Trump delivered a devastating blow to the “Never Trump,” movement, winning easily in Michigan and Mississippi. Given that Marco Rubio had another terrible night—he didn’t pick up a single delegate in either Michigan or Mississippi—Trump looks set to win next week in Florida, where Rubio had been regarded as his closest competition. Doing so would put him in a well-nigh impregnable position in the Republican primary.

By winning two more big states in different parts of the country, Trump demonstrated anew that his coalition of supporters is broader than the ones backing the other Republican candidates. In Mississippi, where eighty-four per cent of Republican voters identified themselves as evangelicals, according to exit polls, he received nearly half of the vote, finishing ahead among voters who identified themselves as very conservative, somewhat conservative, and moderate/liberal. Which is to say: he swept the board. In Michigan, where the Republican electorate was more diverse and included a significant number of independents, Trump got thirty-seven per cent of the vote. According to the exit polls, Trump finished ahead or tied in every age group. He also won in three of the four educational demographics: high-school graduates, people with some college, and college graduates. The only group he didn’t win was postgraduates.

Ultimately, in each state, he finished more than ten points ahead of Ted Cruz, with John Kasich taking third place, and Rubio languishing in fourth. (Cruz later won Idaho, and Trump took Hawaii, with Rubio finishing a distant third in both.)

“I want to thank the special interests and lobbyists. They obviously did something to drive these numbers,” Trump said, during a rambling soliloquy in Jupiter, Florida, after the races in Michigan and Mississippi had been called. He also taunted some of the Republicans who have recently railed against him, including Rubio, Mitt Romney, and Lindsey Graham. Then he did some gloating. “Only one person did well tonight: Donald Trump,” he said.

Although the result in Michigan doesn’t have potentially decisive implications for the Democratic race, Sanders could have contested Trump’s boast. With Clinton racking up yet another big victory in the South—in Mississippi she won more than eighty per cent of the vote—her lead in the delegate count actually increased. But by winning a large majority of white voters in Michigan and eating into his opponent’s hold on the black vote, Sanders delivered a stunning blow to Clinton, and confirmed that his campaign is likely to go all the way to the convention.

The fact that Sanders delivered his statement from Florida rather than Michigan demonstrated that he had exceeded the expectations of his own campaign, which had done polling that showed Clinton with a significant lead in Michigan heading into last weekend. Even as the early returns showed Sanders building up a sizable lead, many of his supporters had feared that Clinton would overtake him once voters from Wayne County, which contains Detroit and its large black population, were counted. But although Sanders’s lead narrowed as the night went on, that didn’t quite happen. Shortly before midnight, the Associated Press and CNN both called the race for him.

Pending a more measured analysis in the days ahead, three factors seem to have put Sanders over the top. Having targeted Michigan with ad dollars and personnel, his campaign did a good job of raising turnout in pro-Sanders strongholds, such as Kalamazoo, Lansing, and Ann Arbor, which have large college-age and post-college-age populations. In the eighteen-to-twenty-nine age group, according to the exit poll, Sanders trounced Clinton, eighty-one per cent to eighteen.

In addition to mobilizing Sanders’s base of young voters, his campaign did a good job of appealing to working-class and lower-middle-class white voters. In the suburbs around Detroit, which have long been known as a home base of the “Reagan Democrats,” and where Clinton did well in 2008, Sanders managed to split the vote roughly equally.

Even more importantly, Sanders managed to limit Clinton’s winning margin among black voters, which has proved decisive throughout the South. According to exit polls, Clinton received sixty-five per cent of the black vote in Michigan, and Sanders got thirty-one per cent. That’s a large difference, but in Mississippi, according to the exit poll, Clinton got nearly ninety per cent of the black vote. Among black Michigan voters under the age of forty-five, the exit polls said, support for the candidates was divided virtually equally: Clinton got fifty-one per cent, and Sanders got forty-nine per cent.

In seeking to explain why Sanders and Trump did so well in Michigan, which has lost hundreds of thousands of manufacturing jobs over the past couple of decades, it is tempting to focus on the candidates’ criticism of trade agreements, such as NAFTA and the proposed Trans-Pacific Partnership. Trump has castigated the politicians who signed these deals, and has pledged to introduce hefty tariffs on goods from China and Mexico. Sanders, in recent weeks, ran ads in Michigan that showed abandoned factories and criticized Clinton for supporting trade agreements. These ads seem to have worked. According to the exit polls, nearly sixty per cent of Democratic voters said they believed that trade costs America jobs, and, among that group, Sanders finished about twenty points ahead of Clinton.

More broadly, it seems that Sanders’s economic populism and Trump’s authoritarian populism both resonated in a state that was hard hit by the Great Recession and its aftermath. Although the messages that the two insurgents are carrying differ wildly in most respects, and shouldn’t be compared in terms of policy content or morality, they both claim that the existing political system is broken, and that radical measures and new leaders are needed to fix it. If this message were to prove equally successful in other industrial states, such as Ohio, Pennsylvania, and Wisconsin, it would have big implications for the general election in addition to the primaries.

Should Sanders win some of these states, it would offset some of the losses he can expect in places with large minority populations, such as Florida and North Carolina. The chances of him closing the delegate gap with Clinton still look slim, but he could remain competitive until the big primaries in New York and California, where he is hoping to pull off more upsets. This calculus may seem unlikely. Until last night, however, it seemed unlikely that he would win in Michigan. “What tonight means is that the Bernie Sanders campaign . . . the political revolution that we are talking about is strong in every part of the country,” Sanders said during his speech in Florida. “And frankly, we believe that our strongest areas are yet to happen.”

Trump, if he does wrap up the G.O.P. nomination in the coming weeks, will be looking to the Rust Belt states come November. As I explained in a post last week that discussed his prospects in a general election, his best hope of winning the Presidency is to carry states like Michigan, Ohio, and Pennsylvania, thus expanding the Republican map. If yesterday is an indication, he’s on his way to expanding turnout, anyway. Compared to 2012, the Republican electorate had increased by more than forty per cent. “I think I am going to win in Ohio,” Trump said. “And then we are going to beat Hillary Clinton, and beat her badly.”

That was Trump’s ego working overtime, of course. But on this night you couldn’t really deny him or Sanders their optimistic outlooks. Populism, after looking like it might have been stymied, was once again on the march.