CEDAR RAPIDS, Iowa (AP) -- White, working-class voters fueled President Donald Trump's rise to the White House. If his party loses the House majority on Tuesday, it will be, at least in part, because those same voters abandoned the GOP.

While Democrats' suburban offensive is well-known, an often-overlooked battle is underway across rural and working-class districts in states including Maine, Iowa and Minnesota. Trump's coalition of blue-collar voters here may offer Democrats an alternate route to the House majority.

Specifically, Democrats are targeting 21 House districts carried by former President Barack Obama in 2012 that shifted to Trump in 2016 — districts now testing the strength of a Trump-era political realignment shaped by education, race and gender.

With the election days away , Democrats have cause for optimism. Public and private polling suggest Democrats are poised to capture at least two-thirds of the Obama-Trump districts, according to operatives in both parties who spoke on the condition of anonymity to speak freely before Election Day.

While Republicans privately blame an underwhelming slate of GOP incumbents, the Democrats' prospective success is a reflection of a strong class of first-time candidates, extraordinary fundraising and a message focused on health care and the economy — not Trump.

In northeastern Iowa's 1st Congressional District, where the cornfields outnumber the Whole Foods supermarkets, 29-year-old Democratic upstart Abby Finkenauer reflected on her blue-collar roots at a rally this week alongside the Democratic Party's strongest liaison to working-class voters, former Vice President Joe Biden.

"He shares the belief that every kid who grows up in a working-class family like mine has a right to a bright future," Finkenauer said as she introduced Biden.

Obama won the district by nearly 14 points in 2012. Trump scored a 3-point victory here four years later.

The 29-year-old state representative, whose father and grandfather were union workers, has made her working-class roots central to the campaign in a district once dominated by union manufacturing and meatpacking jobs. She made a name for herself last year blasting a Republican-backed bill that dismantled public-employee unions, shouting against it near tears on the Iowa House floor in Des Moines.

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"This is personal," she said at the time.

She is facing off against two-term Republican incumbent Rep. Rod Blum, a wealthy businessman.

In working-class southern New Jersey's 3rd Congressional District, Democrat Andy Kim is laser-focused on health care and the Republican tax cuts in his bid to defeat two-term incumbent Rep. Tom MacArthur.

Obama twice won the district, which Trump carried by 6 points in 2016.

Kim, a national security official in the Obama administration, told The AP that he doesn't want to impeach Trump. He condemned the increasingly divisive tone in politics, which he said was a problem long before Trump's election.

The first-time Democratic candidate is eager to bring up MacArthur's votes for the Trump tax cuts and a GOP health care plan that would have replaced the nation's system with one that wouldn't guarantee coverage of pre-existing conditions.

"It isn't politics. It's personal," said Kim, the father of two young sons, noting that his father survived polio and his mother has other pre-existing conditions.

The Republican MacArthur said he was simply working to improve both bills for his constituents. He also recognizes his political challenge in a district that has swung from one party to the other in recent presidential elections.

"A member, to represent this district, can't just be a Trump opposition person," MacArthur said in an interview. "He'll offend half of his constituents. You have to work with the president when you can. You have to have the backbone to push back when you need to."

College-educated voters, particularly women, turned against the GOP long ago. But polling indicates that Democrats' comeback in the Obama-Trump districts, if there is one, will be born of a more subtle shift among non-college-educated white women, according to Jesse Ferguson, who previously led the House Democrats campaign arm.

"If we take the majority, it won't only be built on suburban, Clinton-voting districts alone," he said. "Democrats are winning congressional districts that voted for Donald Trump as people who work for a living see that the Republican majority sold them out."

It's not all good news for Democrats.

In the fight for the Senate majority, Trump's standing remains strong among rural voters in states like North Dakota, Indiana and Missouri where the GOP is on offense.

Republicans have far fewer pickup opportunities in their quest to preserve the House majority. The GOP is on offense, however, in Minnesota's 8th Congressional District, a 27,000 square mile-swath of northern Minnesota where Republican Pete Stauber, a retired policeman, is poised to win a seat left open by a Democratic retirement.

No current district swung more from Obama to Trump. Stauber said the 20-point shift between 2012 and 2016 reflected a political realignment a decade in the making.

"This congressional district is blue-collar common-sense conservative," he said in an interview, noting the presence of a strong mining industry, forestry jobs and the military.

Stauber said he opposed Republican efforts to repeal Obama's health care law and vowed to protect coverage for pre-existing conditions. He also railed against Senate Majority Leader Mitch McConnell's recent suggestion that Republicans would cut Medicare and Social Security to help balance the budget.

"Those are benefits that our seniors were promised and paid into their entire lives," the Republican congressional candidate said. "That's a promise our government made. That's a promise our government will keep."

Polling suggests that Democrats are winning the fight over health care and the economy in other Obama-Trump districts.

They include Maine's 2nd, where Democratic-aligned outside groups have poured money into an advertising campaign railing against incumbent Republican Rep. Bruce Poliquin's health care positions since October 2017.

Trump won the rural Maine district by 10 points in 2016, while Obama carried it by more than 8 points four years earlier.

Democratic candidate Jared Golden, an Iraq war veteran, seized on health care in his closing message.

"When I came home from Iraq, I was diagnosed with a pre-existing condition," the 36-year-old Democrat said in a recent ad. He charged that Poliquin voted with special interests "to allow insurance companies to deny health coverage to anyone with a pre-existing condition."

A Poliquin spokesman declined to respond.

Democrats' strong position has been built, in part, by a fundraising disparity that allowed them to set the terms of the debate.

In just eight Obama-Trump districts across Iowa, Maine, Minnesota, New Jersey and Illinois, Democratic candidates have spent roughly $24 million on TV ads compared to $12 million from their Republican opponents, according to media buyers tracking ad spending.

The super PAC aligned with House Democrats has poured at least another $7 million into the same races.

Though Trump capitalized on the frustration in these districts in 2016, Biden this week welcomed working-class voters back to the Democrats' column with a populist tone.

In Cedar Rapids, Biden said: "I know what built this country: ordinary Americans given half a chance."

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Peoples reported from New York.

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For AP's complete coverage of the U.S. midterm elections: http://apne.ws/APPolitics