Michigan Democrats have a history of surprising everyone in their presidential primaries and caucuses.

In 1972, George McGovern was on his way towards winning the Democratic nomination when George Wallace won Michigan. In 1980, then-President Jimmy Carter was on track when Ted Kennedy won Michigan. In 1988, Michael Dukakis was the favorite to win the Democratic nod when Jesse Jackson won Michigan.

And last night, few expected Bernie Sanders to win the Wolverine State, but that’s precisely what he did. MSNBC’s Alex Seitz-Wald summarized

Bernie Sanders scored a critical upset in Michigan’s Democratic primary Tuesday, winning a narrow victory over front-runner Hillary Clinton in a state where polls had showed him far behind, and proving once again to be competitor when most had counted him out. The Vermont senator is still miles from catching up to Clinton, who won a commanding victory in Mississippi’s primary Tuesday night and holds a significant delegate lead.

By almost any measure, this was Sanders’ most impressive victory to date. While many of his recent wins have come in smaller, less-diverse states – he won in Nebraska and Maine over the weekend, for example – Michigan is a large state with a wide variety of constituencies.

It’s also an upset unlike any we’ve seen in a while. Clinton led in literally every poll out of Michigan, and most surveys showed her ahead by a wide margin. The final FiveThirtyEight forecast said Clinton had a greater than 99% chance of winning.

Even Sanders was probably surprised – he was in Miami, not Michigan, when the results were announced. If he’d expected a victory, the senator likely would have stuck around.

I’ve seen competing explanations for the results, ranging from Sanders’ success in slamming unpopular trade deals to Clinton supporters voting in the Republican primary because they assumed she’d win easily. Whatever the cause, Sanders and his backers have reason to cheer this morning.

But they also have reason to temper some of that enthusiasm with some of the relevant details, most notably the fact that yesterday’s contests actually pushed Clinton, not Sanders, closer to the Democratic nomination.

Upsets are always going to generate more news than expected outcomes, so it’s understandable that Sanders’ surprise win in Michigan is literally front-page news, but it coincided with the Mississippi primary, where Clinton won by an almost ridiculous margin, 83% to 17%. Why does that matter? Because delegates are awarded proportionately in Democratic races, and Clinton’s lopsided landslide in Mississippi ended up benefiting her more than Sanders’ narrow win in Michigan benefited him.

Different news organizations have slightly different counts, but NBC News’ Mark Murray noted this morning that Clinton added 88 delegates yesterday, while Sanders picked up 70. As a result, Clinton actually expanded her overall lead last night among pledged delegates (not including superdelegates), and the race now stands at 761 to 547.

Sanders’ surprise win in Michigan is a big story, which will no doubt help his campaign with fundraising, bragging rights, and possibly even momentum. But at least for now, the math is still on Clinton’s side, and her campaign is well aware of the fact that Sanders would need to win 60% of the remaining delegates to claim the nomination, which is a daunting task.

This not to say Sanders’ upset is inconsequential. On the contrary, the Michigan primary will almost certainly prolong the Democratic contest for quite a while. It will also raise new doubts about Clinton’s polling advantages, especially in nearby states like Ohio.