(CNN)Bernie Sanders teed up the Midwest as a battleground on Tuesday night as he knocked off Hillary Clinton in a down-to-the-wire Michigan primary.
5 takeaways from Tuesday's primaries
Donald Trump, meanwhile, crushed it on the Republican side -- notching wins in Hawaii, Michigan and Mississippi. Ted Cruz picked up Idaho. But Marco Rubio had a night he's just going to want to forget.
Here are five takeaways from Tuesday's contests:
Nobody saw this coming. But the nail-biter in Michigan gave Sanders by far his biggest win of the race yet and put Clinton unexpectedly on defense in a stretch of the campaign she once looked poised to dominate as the Democratic rivals prepare to face off Wednesday night for a debate hosted by Univision and simulcast on CNN.
It's not just the psychological boost (and accompanying likely fundraising boost) of an unexpected win. It's what Michigan portends for Ohio, Missouri and Illinois, which all vote next Tuesday.
For an alleged one-note candidate, Sanders is singing the right tune, especially with his focus on economic injustice. He's giving a home to voters angry over job losses due to trade deals or home foreclosures due to Wall Street's greed.
Clinton's failed attack against Sanders on the auto bailout during Sunday's CNN debate in Flint, Michigan, didn't pass the smell test in an auto-driven state that knows its history. Sanders voted for the auto bailout as a stand-alone measure. What he opposed was a much larger Wall Street bailout later on -- a portion of which included money used to rescue the auto industry.
Clinton's blowout win in Mississippi means she will pick up more delegates than Sanders. And it shows her huge advantage among African-Americans continues to be a firewall she can count on.
But that strength has obscured her weakness among white voters -- which now looks problematic: After Florida and North Carolina next week, the South is done voting.
To see the problem, look at Clinton's calendar. She concentrated nearly all of her five days of Michigan campaigning in Wayne County, the heavily-populated and heavily-African-American home of Detroit. Sanders, meanwhile, competed across the state, and outperformed expectations in other minority-heavy communities.
Donald Trump is eating everybody else's lunch.
He bested Cruz in Mississippi among the two groups the Texas senator had bet big on: Evangelicals, who narrowly went for Trump, and voters angry at government, who gave Trump a two-to-one advantage over Cruz. In Michigan, Trump drowned out Kasich's modest Midwestern job-creating executive appeal, blasting away at trade deals and winning big among the Reagan Democrats he says he can bring into the GOP fold.
Trump bragged in his victory speech Tuesday night that television ads and shots from rivals have done nothing to slow his rise.
"There has never been more money spent on hitting somebody than was spent on me," Trump said. "Every single one who's attacked me is gone, and I'm very proud of that, because that's what we should have for our country."
Brushing aside attack ads aimed at undermining his business credentials, Trump taunted his critics by holding his election-night event at the Trump National Golf Club in Jupiter, Florida -- and catering it with products like Trump wines, water and steaks.
Trump seems able to absorb all the hits and come out stronger. CNN analyst Van Jones compared Trump to an X-Men villain played on film by Kevin Bacon.
"There's a villain in Marvel Comics called Sebastian Shaw, and the harder you hit him, the stronger he gets," Jones said on CNN Tuesday evening. Trump's opponents treated him that way. "You couldn't hit him, don't fight him, knock other people off," Jones said. "We're going to see how many bullets he can eat."
One potentially worrying sign for Trump is that he doesn't win among voters who decided in the last few days. Cruz bested him with those voters in Mississippi. Working in Trump's favor, though, is that those voters haven't yet settled into any specific camp. A week ago, for example, they went to Rubio. In Michigan, it was Kasich gaining steam late.
Hillary Clinton's husband signed NAFTA. She voted for trade deals in the Senate. And she was among the last Democrats to stake out a position on the Trans-Pacific Partnership.
Clinton has nuanced explanations for all of that.
Still, Sanders -- who has raged against all of these deals from the beginning, and features trade as a staple of his stump speech and his attacks on Clinton on debate and town hall stages -- is making her pay for it.
In Michigan, where 15% of all workers are labor union members, 58% of Democratic voters said they believe trade takes away U.S. jobs, according to exit polls. Of those voters, 60% went for Sanders, while 39% went for Clinton.
Similar margins could hurt Clinton in Ohio, Illinois and Missouri next week.
Trade is the single best example of a populist uprising that spans the partisan divide.
Trump's nearly obsessive focus on blasting every U.S. trade deal and everyone who negotiated them guarantees that if he and Clinton are the nominees, this wouldn't just be a problem for Clinton in the primary.
If she advances to face Trump, it'd represent a reversal of modern American politics: An anti-trade Republican against a Democrat much more comfortable with trade.
It's enough to make Reagan Democrats fawn and Chamber of Commerce-types quake.
"We will take many, many people away from the Democrats," Trump said Tuesday night.
Marco Rubio crashed in Michigan and Mississippi, finishing fourth in both. Worse, he didn't get close to cracking the 15% needed in either state to win any delegates.
"It sure looks like a collapse to me," CNN Senior Political Commentator David Axelrod said.
This was supposed to be when Rubio made his move. He's spent two Republican debates unloading everything he had on Trump, while big donors hoisted anti-Trump attack ads onto the airwaves.
Then, the theory went, Rubio would head home to Florida and capture next week's winner-take-all contest and 99 delegates.
Instead, Rubio will only face questions all week about his strategy and what went wrong.
He acknowledged that he's in a fight for his political life Tuesday night in Ponte Vedra, Florida, signaling that he'll hunker down at home.
"I believe with all my heart that the winner of the Florida primary next Tuesday will be the nominee of the Republican Party," Rubio said.
They didn't beat Trump. But they both clobbered Rubio -- and got some news that could help them moving forward.
Cruz picked up Idaho, a reliably conservative state that only has 32 delegates, but lets him continue his argument that he's the top candidate of the #NeverTrump movement.
Among voters who decided whom to support in the past few days, Kasich won the most in Michigan and Cruz won the most in Mississippi. That's a sign both have room to grow, particularly if Rubio loses Florida and is knocked out of the race before it shifts to more moderate Eastern states where Rubio would likely have more support.
Kasich claimed momentum, telling supporters in a late-night fundraising email that "I surged to an unexpectedly strong finish."
Not that he had anywhere to go but up. To date, Kasich's campaign has been about three states: New Hampshire, then Michigan, then Ohio.
It's earned him some jeers from opponents who are running national races. But that strategy -- plus his affable debate-stage demeanor -- have allowed him to avoid other Republicans' targets, too. If he can win the 66 delegate, winner-take-all Ohio next week, he could put himself on a course to rack up enough delegates to be a player at the Republican National Convention in his home state of Ohio.