DULUTH — DFL Gov. Mark Dayton and Republican challenger Jeff Johnson both tried to grab the mantle of middle-class champion Tuesday in a debate punctuated by sharper exchanges than they have shown before.

In the first one-on-one debate of the campaign, Dayton labeled Johnson a “huckster” for promising mining permits on the Iron Range before environmental studies have been completed as a way to endear himself to a Democratic voting stronghold in northeastern Minnesota. Johnson accused Dayton of furthering a philosophy that “government always knows best how we live our lives.”

There were similar scrapes over issues like the minimum wage, transportation, taxes and health care.

Johnson, who hopes to gain ground in a race Dayton leads, was on the offensive from his opening remarks. The Hennepin County commissioner called Dayton a decent man whose privileged roots have shielded him from having to scrimp like many families to pay a mortgage or college tuition.

“When you’ve never had to worry about that in your life, I think it gives you priorities that probably don’t serve the middle-class as well as they could,” he said.

Dayton used his record as governor to combat the charge, saying he’s worked to boost school budgets, freeze college tuition and increase the minimum wage to give struggling families a fighting chance.

“Commissioner Johnson says he’s for the middle class, and then he’s for lowering taxes on the super-rich and lowering the minimum wage for people who are working hard,” Dayton said.

Johnson has said he won’t roll back the prescribed minimum-wage increases but would halt the inflationary hikes.

“This belief the minimum wage is the answer for middle-class families is kind of out of touch with how the middle class lives and what the middle class wants,” Johnson said. “They don’t want low-paying jobs, they want careers in this state and we are not growing them right now.”

The pair often offered competing statistics. Those cited by Dayton — a low unemployment rate and region-leading per capita income — were meant to show a state on the rebound. Johnson’s batch was aimed at demonstrating an economy only limping forward, particularly on new business start-ups and private sector job growth.

“You’re so desperate to find something to make Minnesota look bad that you jump on anything you can find,” Dayton charged.

Johnson shot back: “I never denigrate Minnesota because I’ve spent almost my entire life here. But I certainly think you have us going in the wrong direction.”

The candidates frequently reached back to October debates that included more candidates to accuse one another of shifting stances. That was most apparent on transportation, where Johnson mocked Dayton as having proposed new taxes on gasoline one day only to water his intentions down the next.

Dayton supports tacking a sales tax on gasoline that would be paid at the wholesale level, not on a per-gallon basis. The distinction was murky in the last debate.

“I’m curious, are you going to raise the gas tax or not, because I won’t?” Johnson asked his foe.

“I’m not going to raise the gas tax, but I’m going to face the reality,” Dayton said, adding that it’s “disingenuous” to tell voters a $6 billion transportation project backlog can be addressed by borrowing and squeezing savings out of the highway agency.

It was Minnesota’s first governor’s debate in two decades to feature only two candidates; the Independence Party’s Hannah Nicollet was shut out after taking part in the prior two.