In an hour-long debate Thursday night in St. Louis, Attorney General Josh Hawley tried to use U.S. Sen. Claire McCaskill’s lengthy experience in office against her while she argued that she’s an independent voice who takes on her own party when necessary.

Hawley, a Republican who is less than two years into his first term in public office, repeatedly reminded the audience that McCaskill, a Democrat, has been in politics for 36 years and in her current office for two terms.

“Sen. McCaskill has been in office 12 years in Washington,” Hawley said. “It is just the party line over and over.”

McCaskill began as a state representative and has been Jackson County Prosecuting Attorney and State Auditor in her career.

“I am the fifth most-likely member of the Senate to break with my party,” McCaskill said. “That’s because I look at every issue on its merit.”

The debate was hosted by St. Louis Public Radio, Nine Network and KSDK Channel 5 and moderated by Judy Woodruff, host of PBS’s Newshour program. It mixed questions from journalists and audience members. The debate included only candidates who are polling at 10 percent or above in public opinion surveys and did not include Libertarian Party candidate Japheth Campbell, Green Party candidate Jo Crain or independent Craig O’Dear.

This year’s Senate race in Missouri is one of the most closely watched in the country because McCaskill and Hawley have been virtually tied in polls for months and control of the Senate is at stake. President Donald Trump won Missouri by 19 percent in November 2016 and while his approval ratings have dropped nationally, he retains a net positive rating from Missouri voters.

The most heated exchanges occurred on health care, which the candidates visited often, and questions drew the candidates into topics that included tariffs and the trade war, tax cuts, right to work and immigration.

The debate did not address the enormous sums being spent on both sides, by the candidates and groups on their behalf, that is saturating the state’s airwaves. It also did not address the controversy generated this week by the release of undercover videos attacking McCaskill on gun rights and her support for Planned Parenthood.

Woodruff opened by asking the candidates about the ballooning federal budget deficit and the remarks this week from Senate Majority Leader Mitch McConnell that costs in the Medicare and Social Security programs are “the real drivers of the debt.” The deficit climbed 17 percent to $779 billion during the first full fiscal year under Trump and is expected to increase to $1 billion in the current year and for the next three years.

Hawley, who answered first, said he opposed any cuts to Social Security or Medicare that would change current benefits or change benefits for people who will soon retire. He said the main cause of the deficit was the Affordable Care Act, or Obamacare.

“It has proven to be outrageously expensive for federal taxpayers, but worse it has proven to be outrageously expensive for Missouri families,” Hawley said.

The deficit is expanding because of the tax cuts enacted last year, McCaskill said. The administration claimed the cuts would pay for themselves but corporate revenues are down.

“The Republican Party loves to talk about debt or deficit until they are in charge,” McCaskill said. “Then it is crickets.”

The first audience question was from Maria Watson, who recounted a scary incident involving an active shooter while she was with her 9-year-old son.

McCaskill endorsed a ban on bump stocks, the attachment that allowed a mass shooter to spray bullets in Las Vegas, killing 58 people, in 2017, and expansion of background checks to all gun sales. Hawley, she said, would not support that because it would alienate the NRA.

“There are way too many people, including most of the Republicans, who are way too afraid of the NRA,” she said.

Hawley accused McCaskill of being against Second Amendment rights and said he wanted background checks to include mental health histories.

The debate swung repeatedly to health care, the issue McCaskill has hammered in her ads. As attorney general, Hawley has made the state a party to a lawsuit in Texas challenging again the constitutionality of the Affordable Care Act. If successful, the lawsuit would sweep away the law and all of its provisions, including the requirement that insurance companies cover the costs of preexisting conditions.

Hawley repeated his defense on that issue – he supports legislation requiring insurers to cover those costs but doesn’t want most other parts of the law to survive.

“What we hear from Democrats is a a full-throated defense of Obamacare but nothing about preexisting conditions without Obamacare,” he said.

Hawley is offering nothing that would work to cover preexisting conditions because without the law’s mandate that individuals buy insurance coverage, McCaskill said, insurance companies couldn’t afford it.

“This is so frustrating,” McCaskill said. “He has no plan. He has no plan that will work. All he has out there is a press-release plan.”

When the candidates addressed trade, Hawley defended Trump’s actions that have caused several rounds of escalating tariffs that have cut grain and soybean exports to China and caused farm prices to slide to the lowest levels in recent years.

“We are in a trade war,” Hawley said. “It is a trade war we did not start. Certainly our farmers did not start it. China started it many years ago.”

McCaskill, who called the tariffs “brutal,” went on the attack. Farmers are not going to receive adequate compensation for their losses, as originally promised by Trump, she said.

“Our economy is so dependent on the exporting of commodity goods,” McCaskill said. “There is not a bean farmer in Missouri who is going to come out even this year.”