U.S. Sen. Claire McCaskill speaks to a group of supporters at her Columbia Democratic Party headquarters in Columbia, Mo., on Tuesday, Aug. 7, 2018. (Hunter Dyke/Columbia Daily Tribune via AP)

U.S. Sen. Claire McCaskill speaks to a group of supporters at her Columbia Democratic Party headquarters in Columbia, Mo., on Tuesday, Aug. 7, 2018. (Hunter Dyke/Columbia Daily Tribune via AP)

JEFFERSON CITY, Mo. (AP) — Sen. Claire McCaskill coasted to the Democratic nomination Tuesday in Republican-dominated Missouri, but GOP challenger Josh Hawley could prove to be one of her toughest opponents in a lengthy political career that also included stints as a state legislator and auditor.

McCaskill’s hopes of winning a third term could depend both on convincing voters she’s sufficiently moderate and that Hawley is too closely tied to President Donald Trump, who is supporting him. That’s not an easy task considering Trump coasted to a 19-percentage point victory in the onetime bellwether state less than two years ago. Republicans consider McCaskill one of their top targets nationwide this fall.

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After McCaskill won the primary, she promptly challenged Hawley to four town-hall style debates moderated by local journalists.

“It’s on,” McCaskill tweeted Tuesday in a plea for donations.

Hawley in a statement Tuesday said Missouri voters sent McCaskill “a message” with Trump’s resounding victory in 2016 but that she “was so comfortable in her Washington condo that she couldn’t hear it.”

He’s proposing a series of one-on-one, unmoderated debates that he described as “just me and Claire McCaskill debating on the back of a flatbed truck.”

Retaining seats like McCaskill’s is critical for Democrats if they are to have any chance of gaining control of the Senate, where Republicans hold a 51-49 advantage and have Vice President Mike Pence to break any ties.

“Democrats have to ‘run the table,’” said Steven Puro, a retired political scientist at Saint Louis University. “But the Republicans have a few key states where they think they can build a firewall, and Missouri is one of them.”

The last time McCaskill was on the ballot, she faced Republican Rep. Todd Akin, whose campaign derailed after an interview in which he discussed “legitimate rape” in the context of abortion.

Hawley is a much stronger challenger, and he’s tapping into support from Trump, who has attended multiple fundraisers for him.

“Hawley has clearly hitched his train to the president,” University of Missouri-St. Louis political scientist David Kimball said. “That’s a calculated gamble that overall, the president will help.”

In Trump country, McCaskill often cites the more than 50 town halls she held since 2017 in rural areas of the state. She’s campaigning on issues that could play to both Republicans and Democrats, including health care and drug costs. She has clashed with the president on trade and some other issues, but she also touts areas of agreement with the administration and other Republicans.

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Hawley has attempted to paint McCaskill as a liberal obstructionist, citing her vote against Justice Neil Gorsuch as an example, as well as an out-of-touch elitist. Ads by his campaign and outside groups slammed her for flying on a private plane to some stops on a recent tour of the state in her RV.

Democratic criticism of Hawley has centered on him joining a lawsuit as attorney general against President Barack Obama’s health care law. He has drawn criticism for campaigning against climbing political ladders, then entering the Senate race shortly after taking office as attorney general.

The Democratic Senate Majority PAC has also run multiple ads accusing him of refusing to investigate allegations of corruption related to a top donor to his attorney general campaign, although his office does not have initial jurisdiction in such cases.

Democrats also have attempted to tie Hawley to the state’s Republican former Gov. Eric Greitens, who resigned amid political and personal scandal as lawmakers considered impeaching him.

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Associated Press writer Jim Salter contributed to this report from Chesterfield, Missouri.

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