Rep. Rod Blum (R-Iowa), 63, here addressing constituents in Dubuque in May 2017, is seeking reelection in Iowa’s 1st Congressional District in November. (Scott Olson/Getty Images)

Abby Finkenauer says she’s running for Congress to represent hard-working Iowans who just want “enough money at the end of the week to send their kids to baseball and softball practice and buy a case of beer.”

Rod Blum, the two-term Republican incumbent she hopes to unseat, is a self-made millionaire who often talks about how he grew up in poverty and has criticized fellow members of Congress who use taxpayer money to fly first-class or lease luxury cars.

Both candidates live in this proudly blue-collar city on the Mississippi River in eastern Iowa. And in their battle for Iowa’s 1st Congressional District, both are targeting the voters who flipped the state from supporting President Barack Obama in 2012 to Donald Trump in 2016.

Nearly 40 percent of voters here are not affiliated with a political party, making them unpredictable in this era of sharply partisan politics. The group includes Iowans who are fed up with the federal government, tired of gridlock in Congress and distrusting of the major political parties. They are credited with playing a major role in Trump’s victory in the district and are expected to decide this fall’s midterm elections in the state.

Of the 20 counties in Iowa’s 1st District, 15 moved from Obama to Trump. More than 200 of these “pivot counties” exist nationwide, but they are heavily concentrated in the Upper Midwest. Political strategists are watching voters in these counties for clues about how they might vote in future elections and what messages from candidates they will find most compelling.

To attract those elusive voters, Blum and Finkenauer are operating from different perspectives to focus on the same themes: economic issues such as higher wages and cheaper health care, and what they contend is their personal distance from party leaders and Washington politics.

State Rep. Abby Finkenauer (D), 29, will face Blum for Iowa’s 1st Congressional District seat in November. (Lauren Justice/For The Washington Post)

Blum has been traveling through the district to promote the booming economy and the Republican-pushed tax cuts. He has said he plans to continue focusing on cutting government spending, eliminating the federal deficit, reducing taxes and cutting regulation on businesses. He supported efforts to repeal Obama’s Affordable Care Act.

Finkenauer argues that ­middle- and working-class Iowans are still suffering financially and that the tax cuts have benefited the wealthy more than them. She has targeted union members and blue-collar workers, and she talks about many of the issues Trump once did, including making health care more affordable, increasing the number of higher-paying jobs, rebuilding the state’s infrastructure and expanding job-training programs.

Dubuque County is mostly white and home to more than a dozen Catholic churches, five religiously affiliated universities, a sprawling John Deere factory and hundreds of farms. About 60 percent of residents live in the city of Dubuque, with the rest in bedroom communities and rural towns.

Obama won Dubuque County by double digits — but Trump barely eked out a win. Republicans are hopeful that the area’s recent move to the right has been cemented, while Democrats hope 2016 was a fluke.

“I think they can be won back over,” said Roger Oberbroeckling, 56, the Democratic mayor of Luxemburg, a small farming town at the western edge of Dubuque County where Republican Mitt Romney in 2012 received 187 more votes than Obama — and where Trump received 566 more votes than Hillary Clinton.

Three in 10 of the district’s voters are Democrats, and a near-equal proportion are Republicans. The independents who control the elections often lean left in urban areas such as Dubuque and Cedar Rapids, and right in more rural areas.

But beyond that, little is known about these voters, said Christopher Larimer, an associate professor of political science at the University of Northern Iowa who has studied the district’s voters.

“We don’t know how those no-party voters feel — and if there’s a difference between being a no-party voter in Clayton County versus Dubuque County or Black Hawk County or Linn County, in the more urban areas,” Larimer said, listing counties in the 1st District.

Blum hosts a town hall meeting in Cedar Rapids, Iowa, in May 2017. (Scott Olson/Getty Images)

Iowa Republican leaders suspect that many independents are conservatives who usually vote for Republicans, even if they do not identify with the party. Finkenauer’s campaign thinks that many of these voters are working-class folks who are tired of hearing so much about Trump and are annoyed with national politics.

For Blum, who made his fortune by starting a software company, success will mean connecting with those who fully support the president’s agenda and those who worry the president is governing somewhat recklessly — the latter group including farmers and producers who could be financially hurt as a result of Trump’s trade policies.

Blum recently described farmers who suffer financially for the good of the country as “patriots,” an argument that has been made by Trump. Blum often sounds like the president as he declares his disdain for “the swamp” and “career politicians.” He stormed out of a television interview last year because he thought the questions were unfair.

Blum said economic successes under Trump are being celebrated by all Iowans, including independents.

“Their job security is greater because the companies they are working for are doing better,” said Blum, 63, a member of the conservative House Freedom Caucus. “So people feel very good. The optimism is very high about the economy.”

Finkenauer has what may be a more difficult task: to appeal to Trump supporters, including no-party voters and even some Republicans, without alienating Democrats who are angered by Trump’s presidency.

“Folks are waking up and realizing, ‘Wait, we’ve got to make a change here,’ ” said Finkenauer, 29, who was elected to the Iowa statehouse the same year that Blum was elected to Congress. “And I think there was a change that needed to be made in 2016. It just wasn’t exactly the right change.”

The two candidates’ targets within the swath of independent voters dictate somewhat different pitches.

Finkenauer’s campaign office in Dubuque on June 4. (Lauren Justice/For The Washington Post)

Blum has tried to underscore his blue-collar bona fides with populist flair, pitching himself as an “independent voice for Iowa.” He sometimes shadows constituents to learn what it is like to deliver mail and packages, work as a bank teller or patrol a police beat. Last month, he put on a red Budweiser polo shirt, hopped in the cab of a Bud Light semi and helped a local beer distributor make deliveries.

He distances himself from the Washington in which he serves by bragging that his first vote in the nation’s capital was to strip Rep. John A. Boehner (R-Ohio) of his speakership. He recently voted against the omnibus spending bill that his party’s leadership introduced.

In January, Blum introduced legislation that would cut congressional pay if the budget is not balanced and forbid members to use taxpayer money to lease cars or fly first-class. He has called for congressional term limits and promised to term-limit himself, although he has yet to say when he would depart.

Even as he uses decidedly Trumpian rhetoric, he insists he is a free agent.

“I stand up to the swamp a lot,” Blum said in a telephone interview as he drove from one end of the district to the other. “I think people in Iowa respect that I’ll take a stand, even if it’s against the president of United States or my own party.”

Finkenauer also declines to endorse her party’s leaders. She will not say whether she would vote for Rep. Nancy Pelosi (Calif.), the House Democratic leader, for speaker if Democrats regain control of the chamber.

“No one from Iowa has ever asked me the question, because no one talks about it here, and no one cares,” Finkenauer said in an interview next to a fishing pond in her parents’ back yard. “I’ll be frank: Nobody has my vote until I get there and I sit down with them and we have a long conversation about my district and about the folks in it.”

Her pitch touches close to home. Finkenauer is still paying off the student loans she needed to attend Drake University in Des Moines. Her father worked for years as a union pipe fitter. Her sister and brother-in-law grow soybeans and are worried about the brewing trade war.

The 2018 race “is not going to come down to whether you’re a Democrat or a Republican,” Finkenauer told her supporters at a Dubuque bar after easily winning the Democratic primary on June 5. “It’s going to come down to whether you care about people or not.”

An evocative campaign commercial shows Finkenauer walking through an industrial warehouse.

Heavy-equipment maker John Deere has a major factory in Iowa’s Dubuque County, which is in the 1st Congressional District. Dubuque County twice backed Barack Obama for the presidency but pivoted to Donald Trump in 2016. (Lauren Justice/For The Washington Post)

“You want to know what tough is? Wringing the sweat out of your belt,” Finkenauer says, describing something that she once saw her father do after working a long shift in the summer heat.

The commercial features a feast of blue-collar images: welding sparks, her father in his workshop, a big American flag, a cold beer being poured into a glass, a woman balancing her checkbook, a farmer in bib overalls, and family friends standing in front of a small brick church.

This competitive race is likely to cost millions. In 2016, spending in the district topped $6.5 million. The House Majority PAC, which supports Democratic congressional candidates, has reserved $540,000 worth of television ads. The Congressional Leadership Fund, which supports Republican candidates, has opened a field office in the district and is targeting conservative voters who have grown cynical and otherwise might not vote this fall.

Iowans do not seem especially eager to confront the choice.

In the city, yards sport far more signs related to local races for county supervisor and county attorney than for Congress. The day after the primary election, the front page of the Telegraph Herald in Dubuque focused on those races.

Finkenauer’s photo and name were relegated to the side, under a small heading that read: “Other primary winners.”

A view of the Mississippi River in Dubuque. (Lauren Justice/For The Washington Post)