GEOFF BENNETT: It's been more than a decade since Iowa has had a Democratic governor or senator, but this year, with the incumbents retiring there, both races are competitive.

As Peter Tubbs of Iowa PBS reports, record high diesel prices have hit the state's agricultural industry especially hard and could influence the results.

PETER TUBBS: The ongoing war in Iran may be influencing the midterm elections in the Corn Belt.

Over the last eight months, farmers have seen the price of inputs go up, including a doubling of diesel fuel prices.

The increases are squeezing producers already up against tight profit margins.

AARON LEHMAN, Iowa Farmers Union: Whether that is seed, whether it's chemicals, whether it's repair costs, labor costs, right after the war, the prices for fertilizer and diesel spiked dramatically, and we have seen that continue all the way through to our inputs for harvest and what -- the fertilizer for next year.

PETER TUBBS: Aaron Lehman is president of the Iowa Farmers Union.

He's spending an additional $1,000 day to harvest and transport his crop, double his costs from 2025.

The fertilizer that fed his corn crop this season now costs 75 percent more than a year ago.

The topic of diesel prices and the pressure on farmers led off a debate between Iowa's U.S.

Senate candidates.

REP.

ASHLEY HINSON (R-IA), Senatorial Candidate: You talk about farmers and how we can help them.

It is about their bottom line and doing whatever we can to reduce energy costs, input costs across the board.

So I have proposed a several point energy plan, diesel prices being the top of mind there.

JOSH TUREK (D), Iowa Senatorial Candidate: When I'm out there with farmers, and especially at harvest time, talking about an all-time high of diesel, this is because of this war in Iran, and a war that Ashley Hinson has voted in favor of seven times.

It is hurting Iowans and it's hurting Iowa's in a unique way, and we need to provide some relief to Iowans.

PETER TUBBS: Lehman believes the jump in diesel and fertilizer costs are direct result of President Trump's war in Iran.

The White House announced this week an $8 billion bailout for farmers experiencing high diesel costs.

But high fuel prices could be a reason rural Americans, many of whom have supported Trump's policies, will vote against the Republicans on this year's ballot.

After being a swing state for decades, Iowa has voted for Republicans at the federal level the last two election cycles.

In a break from tradition, the Iowa Farmers Union has endorsed all the Democrats running for Congress.

AARON LEHMAN: That's unusual for us, but our farmers are facing such a huge crisis.

We really expect to have an Iowa response to that.

And this is meant to say we need a stronger response to what we're feeling here out on the ground.

PETER TUBBS: The Iran war and the rising price of diesel is being felt by farmers across the heartland.

In Kansas, the U.S.

Senate race is a toss-up, with incumbent Republican Roger Marshall facing a strong challenge from Pastor Adam Hamilton.

If Hamilton wins, he'd be the first Democrat to represent the state in nearly a century.

Despite the impact on his farm, Ron Suppes says he supports the Trump administration's war in Iran and will vote for Marshall.

RON SUPPES, Wheat Farmer: I'm going to tolerate it until the end.

I don't think it'll last that long.

I think it'll be over pretty soon.

I'm surprised that all of this happened before the election, but I think they ran into a situation where we need to do something now or never.

PETER TUBBS: Back in Iowa, agriculture represents only 3 percent of the state's economy, but farm business sets the political and emotional tone.

Low profits on Iowa's farms have a ripple effect to the economy as a whole.

It's part of the reason economic growth in Iowa has lagged behind its six neighboring states and the country at large for a decade.

AARON LEHMAN: I think people are really starting to have a conversation.

And a lot of people are saying, I need to reconsider.

PETER TUBBS: For the "PBS News Hour," I'm Peter Tubbs in Alleman, Iowa.