Republican Zach Lahn and Democrat Rob Sand repeatedly returned to one topic in their first debate Tuesday night in the race to be Iowa’s next governor: questions about Lahn’s residency history in the state.

Sand, the state auditor, and Lahn, a businessman, met in Davenport as they run to succeed retiring Republican Gov. Kim Reynolds in an unusually competitive race for a state that has trended to the right in recent years.

Iowa has not had a Democrat in the governor’s mansion since Chet Culver was defeated in 2010, and Sand is the only Democrat currently elected statewide. While Sand has cast himself as an independent-minded candidate, Lahn labeled him a “radical liberal” and a “career politician” who supports liberal positions on taxes and immigration.

As the two men sparred over tax rates, economic growth, addressing the state’s cancer crisis and other issues on NBC affiliate KWQC, both repeatedly referred to the controversy over Lahn’s reported ties to Kansas, which include public records showing he voted there in 2018, 2020 and 2022 before he registered in Iowa in 2024.

Lahn responded Tuesday to reports that he still frequently flies to a second home in Kansas.

“I’m a sixth-generation Iowan. I live in Iowa today. I have lived in Iowa. Rob has been lying about this, and the issue is I have a blended family, and my kids split time,” he said.

The subject first arose in a conversation about education. Sand advocated for increasing teacher salaries and better oversight of the use of public funding, while Lahn called for stronger auditing of the school voucher system and limiting the program to lower-income families.

“I want to be the biggest advocate for public school kids in the state,” Lahn said.

Sand responded: “I don’t think you’re going to be the biggest advocate for public school students over a guy who sends his kids there. When you were running advertisements saying that Marxists have hijacked the curriculum in Iowa, Zach, I’m pretty sure that that’s just more evidence that you don’t spend enough time in Iowa.”

Lahn called the attacks “the central lie of Rob Sand’s campaign.”

The controversy has been a drag on Lahn’s campaign, with Sand holding an advantage in public polling ahead of November’s election.

Throughout the debate, Lahn lambasted Sand as a “liberal billionaire” backed by his wife’s family’s money.

Sand’s wife, Christine, is the CEO of her family’s company, the Lauridsen Group, which owns several food and health product companies. Her family has donated more than $12 million to Sand’s campaigns over the years, having backed him since he first ran for state auditor.

Earlier in the night, the candidates were asked how they would address Iowa’s low economic growth rate and the question of affordability on Day 1 in office.

Lahn said he would prioritize homegrown businesses and make sure state government was “not prioritizing big out-of-state projects that are not employing people, like data centers.”

He did indicate he would support tax incentives for the White House-backed $15 billion steel mill project announced last week. He also praised President Donald Trump’s executive action loosening restrictions on tax-exempt “red dye diesel” fuel used for farm vehicles, which he said he proposed to Vice President JD Vance when he visited Iowa last month.

The rising cost of diesel, now $6.05 per gallon in Iowa, has been a major concern for farmers in the state, who have also felt the squeeze from rising fertilizer prices and tariffs, threatening the campaigns of GOP candidates in the heartland.

Sand called for a cap on utility fees, ending the privatization of Medicaid in Iowa, raising the minimum wage — which he has said should be set at $12 an hour — and importing prescription drugs from Canada.

Lahn wouldn’t commit to raise the minimum wage, which was last raised in Iowa in 2009 and is at $7.25 an hour. He said he would focus on industry deconsolidation and lowering taxes.

“We’ve had some great efforts to lower taxes for the people of Iowa, and Rob, you’ve opposed those efforts at every step,” Lahn shot at his opponent. “And so I think we have to be very honest here about where we’re standing. Rob is supporting the raising of taxes because that’s what liberals do: They want to raise taxes. I’m here to cut taxes.”

Asked to respond, Sand denied that he wants to raise taxes.

Both candidates made a point to address cancer rates in their opening statements. Iowa is one of three states where the incidence of cancer is increasing amid environmental risks associated with chemicals used by the agriculture industry, like glyphosate, PFAS and nitrates.

“Iowa is at a point where we are at the bottom for economic growth; we’re at the top for cancer growth,” Sand said.

Lahn cited “the fastest rate of new cancer in the country” as one of three issues that motivated him to run for office.

Lahn, who is backed by prominent members of the “Make America Healthy Again” movement, has made cancer rates a centerpiece of his campaign, frequently targeting the powerful agriculture industry. He called addressing cancer a “foundational question” and the “crisis of our generation.”

“For a very long time, we have seen the nitrate load in our water increase year after year,” he said. “We have to start to put in place real solutions.”

He voiced support for the state’s IWiLL program (Iowa’s Water and Land Legacy) to address water quality issues and high nitrate levels.

“I’m glad that Mr. Lahn brought up IWiLL and mentioned that he’s been supporting it and talking about it since he started the campaign. I’m glad that he’s been doing that,” Sand said. “I actually voted for it in 2010 because I lived here. You didn’t.”