The trade winds were behind Sen. Bernie Sanders' in Michigan's 2016 Democratic primary on Tuesday, leading him to his biggest win of the cycle so far.

The results were quite the surprise, considering that Clinton had enjoyed huge margins in the polls there. The Real Clear Politics poll average coming in had her with a 21-point lead; Huff Post pollster had her up 18 points.

Previous Sanders wins had been, if not exactly expected, as least entertained in the days prior to voting. This one is an upset, no two ways about it. Polling guru Nate Silver called it "among the greatest polling errors in primary history."



In many ways, the outcome is validation that Sanders can contend in the Midwest with his strategy of honing in on free trade, which he has been doing in a big way recently. Just look at this tweet:

The people of Detroit know the real cost of Hillary Clinton's free trade policies. pic.twitter.com/OoatUvhEc9 — Bernie Sanders (@BernieSanders) March 3, 2016

He hammered home the same theme during Wednesday night's debate, saying, "Secretary Clinton supported virtually every one of the disastrous trade agreements written by corporate America. … Look, I was on a picket line in early 1990s against [the North American Free Trade Agreement] because you didn't need a PhD in economics to understand that American workers should not be forced to compete against people in Mexico making 25 cents an hour."

Among the 60 percent of primary voters in Michigan who said free trade takes away U.S. jobs, Sanders won by 13 points. And he won among those voters who decided in the last week. There's little evidence Clinton's gambit to tie him to a vote against the money that went toward bailing out out the auto industry had any effect.

Trade is certainly a weak area for Clinton; she dithered over the Trans-Pacific Partnership, only coming out against it in a way that looked like it was solely a reaction to Sanders, and she supported NAFTA in the '90s. (To be fair, as she noted in the debate, she voted against the only trade pact to come before her when she was a senator, the Central American Free Trade Agreement.) Sanders picked her apart on the issue in Michigan, as, presumably, will Donald Trump, should she and the orange one win their respective nominations.



Sanders now has to be looking ahead to states like Ohio and Illinois, which vote on Super Duper Tuesday, and thinking he has a real shot. But he still has a delegate problem. And it showed up on Tuesday, again, in the deep south.

In the night's other Democratic primary, as expected, Clinton cruised in Mississippi. She has overwhelmed Sanders all across the South, in states such as Alabama, Arkansas and Georgia. There, Sanders' deficit with black voters has been starkest, and it was the same story in the Magnolia State, where Clinton received 90 percent of the black vote. And she's going to run up a big delegate margin because of it.

Sanders, of course, had a decent weekend prior to Tuesday's voting, winning three of the four contests – he came out ahead in Kansas, Maine and Nebraska, losing only Louisiana. Despite his victories, though, he barely made any headway into Clinton's delegate count, reducing Clinton's nearly 200 pledged delegate lead by just two, according to the New York Times.

