Democratic front-runner Hillary Clinton meets with medical professionals at Cooper University Hospital’s MD Anderson Cancer Center in Camden, N.J., on May 11. (Melina Mara/The Washington Post)

Facing the unpredictable candidacy of Republican Donald Trump, Democratic front-runner Hillary Clinton is preparing to dispatch resources to vote-rich industrial states that have been safely Democratic for a generation.

Clinton’s plans include an early, aggressive attempt to defend Pennsylvania, Wisconsin and Michigan — reflecting a growing recognition inside her campaign of the threat that Trump’s unconventional bid for president may pose in unexpected places, particularly in economically struggling states that have been hit hard by global free-trade agreements.

Joel Benenson, Clinton’s chief pollster and senior strategist, acknowledged that Trump’s popularity, particularly among white, working-class voters, could make states in the country’s industrial midsection more competitive than they have been in recent elections.

“There is no state where they can put us on defense that we don’t already treat as a battleground,” Benenson said. He added: “The key here is to really protect the territory we have to protect, then play offense.”

Clinton performed poorly against Sen. Bernie Sanders of Vermont in Democratic primaries in this part of the country — partly because of her past support for free-trade agreements and partly because Sanders’s promises to focus on economic issues and income inequality resonated with voters. Those factors could work against her with Trump, who has criticized her positions on trade and has also found deep appeal among the working class.

Clinton’s team expects the fiercest battlegrounds of the past several elections — including Virginia, Florida and Ohio — to play an outsized role in 2016. But her campaign is preparing to invest heavily in states that President Obama won in 2012, if not always by large margins.

Take Michigan, a state that Obama won twice despite investing little in 2008 and 2012. Michigan Democrats say that Trump poses some “challenges and opportunities” that make this year different.

“We’re looking at it as kind of unique,” said Brandon Dillon, chairman of the Michigan Democratic Party. “He’s unconventional and will say anything to any audience to get the support he’s looking for.

“We believe Michigan could be a battleground state, given what Trump has said and this kind of appeal that he’s trying to make to white, working-class voters about the economy,” Dillon added.

Clinton’s campaign is hiring staff and opening field offices in Michigan, although Dillon said that, until recently, the protracted Democratic primary has delayed any serious organizing efforts by national Democrats.

Campaign staffs also are being dispatched to Ohio and Wisconsin. And in Pennsylvania, much of Clinton’s primary staff and infrastructure are staying put and transitioning to the general election — including her state director in the primary, Corey Dukes, a former aide to Sen. Claire McCaskill of Missouri.

Although many Democrats question whether Trump’s well-documented strength with white, working-class voters will hold true in the general election, there may be no better place for him to test the possibility in November than in the industrial upper Midwest.

“If we believe that he’ll have an unusually high level of appeal to the white working class, then these states are dominated by white, working-class voters. And therefore, if he can move enough of those folks, he might have a chance,” said Ruy Teixeira, an expert on political demography at the liberal Center for American Progress. “It’s not crazy, it’s just not easy.”

Republicans also see the opportunity for strong performances in unexpected places this year. Stephan Thompson, a senior aide to Wisconsin’s Republican Gov. Scott Walker, said that his state still leans blue in general elections, even this year — but he also thinks Trump has the potential to continue defying conventional wisdom.

“When you look at where he did well in the primary in Wisconsin, which was in rural areas, northern and western in Wisconsin — those are places that George W. Bush and Mitt Romney struggled in,” Thompson said. “If Donald Trump can put those voters in play . . . there’s an opening. But he has to shore up traditionally Republican base voters in the suburban areas.”

He added: “Nobody unifies Republicans more than Hillary Clinton.”

A struggle over trade

For Clinton, the threat Trump poses in industrial states such as Wisconsin and Michigan may be compounded by her own weaknesses there; she lost both states’ Democratic primaries to Sanders.

Democrats say that Clinton will need to work assiduously to court Sanders’s supporters in these parts of the country — including younger millennials and working-class voters concerned about economic fairness but also frustrated with government.

In Wisconsin, younger voters at or around the University of Wisconsin in Madison — who supported Sanders heavily in the primary — are a critical part of the coalition, according to Dan Kanninen, who was Obama’s Wisconsin state director in 2008.

“She’s got to reach out to them and really focus on connecting with people who didn’t grow up knowing who the Clintons were,” he said.

Democrats including Obama, Sen. Elizabeth Warren of Massachusetts and Vice President Biden are expected to help with that effort in a general election.

“Low enthusiasm on the Democratic side, high enthusiasm on his side, winning over lots of men and winning over rural voters — that’s the case for Trump,” Kanninen said. But given the antipathy toward Trump among establishment Republicans in the state, he added that Trump will have trouble unifying his own party.

At the heart of Clinton’s struggle with Sanders has been her support for free-trade agreements — a weakness that could hurt her against Trump, too.

“Whatever the numbers say, people don’t feel as economically secure as they did, say, in the 1990s,” said Joe Zepecki, a former communications director for Obama’s 2012 Wisconsin campaign. “What people are looking for is someone who they can trust and who will work hard on the issues they care about. And I believe Secretary Clinton can make that case.”

But he added: “Put me down as nervous and wanting to make sure that the Clinton campaign gets it right.”

After Clinton’s loss in Michigan, the campaign refocused her economic message in Ohio on trade and manufacturing jobs. She defeated Sanders by a large margin in the Ohio primary.

Clinton is planning a similar strategy with Trump — focusing on the government’s role in boosting job creation, with a heavy emphasis on Trump’s statements opposing a higher minimum wage and unions generally.

“We’re going to do better with white, working-class voters than people anticipate,” said Rep. Tim Ryan (D-Ohio), a Clinton ally. “Donald Trump is pushing very hard for right-to-work legislation, he’s said wages are too high . . . he should be very, very concerned about that.”

Ryan continued: “The female independents and moderates both male and female — Trump is just not going to resonate with them at the end of the day. They don’t want somebody yelling and screaming at them. They’re going to want someone who can put things together.”

Trump’s potential to resonate among voters in communities hit hard by a lagging economy extends to parts of southwestern Pennsylvania surrounding Pittsburgh, where Democrats see a special need to focus on steering voters away from Trump.

“From a straight-up policy perspective, Donald Trump is on exactly the wrong side of issues for a lot of people who are turning up and supporting him,” said T.J. Rooney, a former state representative in Pennsylvania and former chair of the Pennsylvania Democratic Party. “Voters are not focusing in on exactly what it means for Pennsylvania and how Donald Trump’s views on the economy might not meld with theirs.”

“It’s going to take time to convince folks who are overlooking obvious deficiencies,” he added.

Elsewhere, the Clinton campaign will be focused intently on maximizing her potential advantages among more reliably Democratic voters, including those who are nonwhite, college educated and women across the socioeconomic spectrum.

The extended Democratic primary has frustrated party leaders in battleground states who are eager to get to work. Campaign aides say that Clinton is contesting Sanders in the primary while also delivering a broader message to suburban voters, particularly women, by focusing on issues including pay equity and child care.

“For every person that Donald Trump appeals to with his economic message, which is entirely unrealistic but sounds good when you hear it, he turns off a lot of suburban, Republican-leaning women and men,” said Dillon, the Democratic chairman in Michigan. “It’s about making sure that people understand the product that Donald Trump is selling is really fool’s gold.”