Democratic presidential candidate, Sen. Bernie Sanders, I-Vt. acknowledges his supporters on arrival at a campaign rally, Tuesday, March 8, 2016, in Miami. (AP Photo/Alan Diaz)

Sen. Bernie Sanders (I-Vt.) scored a narrow but unexpected win in the Michigan Democratic primary Tuesday night, in part because of two factors: trade and trust. Clinton did not have a disastrous night overall; she won Mississippi by a huge margin, which helped her delegate count. The math still strongly favors Clinton to win the Democratic nomination. But Sanders has exposed some big weaknesses that will dog Clinton in the rest of the primary campaign — and probably in the general election, too.

First, Sanders savaged Clinton on trade. At Sunday’s Democratic debate, Sanders railed against NAFTA and other supposed heresies Clinton’s husband committed in the 1990s. This may have proven quite effective. According to exit polls, 58 percent of Democratic voters said that trade “takes away U.S. jobs,” and 56 percent of them voted for Sanders. Sanders also won with people who are “very worried” about the economy. His simplistic populism, with a slightly stronger emphasis on trade, turned out to be the winning narrative in Rust Belt Michigan, and it will no doubt help him in big upcoming states such as Ohio.

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

Clinton has attempted to neutralize the trade issue, coming out against the Trans-Pacific Partnership (TPP) trade agreement at the start of the campaign. But the Michigan exit polls indicate that many voters also believe that Clinton is untrustworthy — or at the very least that they think Sanders is more honest. A quarter of Michigan Democratic primary voters said honesty was the most important quality in a candidate, and 80 percent of them supported Sanders. He seems authentic. She does not. This has not changed.

To an extent, these voters have a point. Clinton would probably favor striking trade deals with foreign countries, and her late opposition to the TPP is probably mere pandering. Clinton should have been less of a weathervane on TPP. But they are wrong to oppose trade deals, which benefit U.S. exporters and consumers. The TPP, moreover, represents an American commitment to an essential part of the world. Sanders appears to be benefiting from the elements of Trump-like populism that play among some Democrats and independents voting in Democratic primaries, including mistrust of foreigners stealing American jobs.

That dynamic should worry Clinton for two reasons. First, Donald Trump and Ted Cruz, the two most likely GOP presidential nominees, both oppose the TPP. Trump has attacked trade deals from the start of his campaign. Cruz is on slightly shakier ground because he had to flip-flop in order to vote against giving President Obama “fast track” trade authority. But he still found his way to voting “no.” In a matchup against Clinton, either of them could make a play for Sanders populists. This may well not be enough to offset the advantage she would have among minority voters, but it is a danger. Second, if Clinton does win the presidency, protectionist sentiment may constrain her from pursuing an assertive international agenda. The following might be terrible political advice — but it would be nice if she would make the argument for broader economic engagement rather than shying from it and still losing.