Heidi M. Przybyla

USA TODAY

Hillary Clinton’s problem nailing down the Democratic nomination has everything to do with the economy, stupid.

That's the message — keying off a phrase her husband’s campaign used successfully in 1992 — that Michigan voters just delivered in giving Vermont Sen. Bernie Sanders a stunning upset victory earlier this week.

Sanders, who narrowly beat Clinton in the Great Lakes state, can now use that momentum to potentially challenge her in other Midwestern industrial states that vote on Tuesday.

Both Democratic presidential candidates warn of a nation where the children of today will have a lower standard of living than their parents. And it's on that concern, over a growing income divide, that Sanders won the economic argument.

Stephanie Gerber, a 35-year-old hairdresser from West Bloomfield, said good-paying union jobs with health and pension benefits are a relic of the past. “Most of our representatives are making decisions based on lobbyist and corporate money, and I don’t feel like they’re making decisions in our best interest anymore,” said Gerber.

Clinton’s challenge in Ohio, Illinois and Missouri is crystallized by Michigan exit polls. While she has a slight advantage over Sanders among voters worried about the economy, Sanders appears to have won among the so-called struggling middle class vote. The two ran about even among the lowest-income voters — those earning less than $30,000 a year — and the highest earners, according to exit polls. Yet 54% of those earning between $30,000 and $50,000 annually backed Sanders, giving him a 10-point edge. Among those rating income inequality the most important issue, he blew her away by 22 points.

For Sanders, "bad trade deals" are a visceral part of his platform, and the data suggest that paid off. Almost three out of five Democratic voters said trade takes away jobs, and he had a 15-point advantage with this group.

Christine Morse, a 42-year-old homemaker from Kalamazoo, said her father worked his way up from assembly line worker to supervisor at General Motors Corp. without a college degree. “You can’t do that anymore and everybody knows it,” said Morse. “These are my people, and they’ve been left behind as the corporations just make more and more and more money.”

Both Gerber and Morse voted for Sanders.

Top takeaways from Michigan, Mississippi and Tuesday's other contests

As the race moves to a cluster of industrial states, in addition to Florida and North Carolina, Clinton’s strategy is two-part.

First, she’s distancing herself from her husband’s 1990s-era trade policies, pointing to her Senate record. Clinton has said she rejected a Central American trade pact, the only multilateral trade agreement during her eight-year Senate tenure. She’s also calculating that her policy proposals, more detailed than what Sanders has offered, can achieve what they failed to in Michigan: overcome the raw emotion Sanders is tapping with his anti-trade message.

Rep. Tim Ryan, who represents the Akron and Youngstown areas of Ohio devastated by manufacturing job losses, huddled with Bill Clinton and other campaign surrogates Wednesday night in Dayton. He said the Clinton campaign will emphasize proposals to boost U.S. industrial jobs, including a manufacturing tax credit, a “clawback tax” that penalizes companies that ship jobs overseas and a proposal to discourage corporate inversions.

Hillary Clinton's public events, including a Saturday visit to St. Louis, will emphasize a “new bargain” for better paying jobs including carpenter apprenticeships.

While Ryan himself won his congressional seat in part on an anti-trade message, he says those aged 30 to 45 now want concrete solutions. “I don’t want to have another discussion about how bad NAFTA was,” said Ryan. “Maybe we didn’t do a good enough job in Michigan explaining what her plans for the future really are,” he said. But, “in Ohio they’re hitting that cord.”

“Bernie does a nice job of identifying the problem, but very few specifics on, now what?” said Ryan.

Yet the hollowing out of the U.S. manufacturing industry and the perception that it is largely due to trade policy has had more than two decades — since the North American Free Trade Agreement was enacted — to marinate in the nation’s industrial heartland.

And for voters like Meredith Buckley, a 33-year-old administrative assistant from Waterford, Mich., it’s personal. In 2008, she lost her job at an automotive supplier, commencing a two-year spiral of unemployment. “It definitely affected me,” she said. “I couldn’t even get a lot of minimum wage jobs because they saw I went to college.”

She voted for Sanders, she said, in part because of the trust issue. “I don’t know that she’d follow through on penalizing companies because she takes so much money from them,” said Buckley.

There are many voters like her in Ohio, said Jeff Rusnak, Sanders’ state director. “Ohio is Michigan on steroids,” he said, citing more than 300,000 manufacturing job losses over the past couple decades, including plants that once produced popular brands such as Dirt Devil, Mr. Coffee and Hoover.

As in Michigan, the Sanders campaign has been working aggressively in the state for some time and polling seems unreliable. One recent survey gives Clinton a nine-point advantage and another a 30-point lead.

USA TODAY's 2016 Presidential Poll Tracker

“The line from Toledo to Youngstown, where a vast majority of the voters are going to come from in the primary, is majority blue collar,” said Rusnak.

The Clinton campaign is downplaying expectations after Sanders’ successful night that followed polls showing him down by as many as 20 points in Michigan.

“The demographics of those states are similar to Michigan,” campaign manager Robby Mook said in a Wednesday conference call with reporters. “All signs point to Sen. Sanders competing especially hard.”

Yet they’re also arguing that they’ll defeat Sanders by attrition, or by picking up an overwhelming number of delegates in states where she’s strong and neutralizing him in states where he may have the advantage. Currently Clinton has a lead of about 200 pledged delegates.

And the campaign is confident her proposals to lift the manufacturing sector will give her a boost.

Some Michigan voters, though, saw the campaign as being about more than just policy prescriptions.

“This isn’t an election,” said Kelly Collison, a 27-year-old pharmacy technician, from Lansing. “This is a movement, this is a revolution.”

Elections 2016 | USA TODAY Network