CONWAY, Mo. — “No, no, no,” Josh Hawley said, suddenly animated. “No. No. No. Not on the agenda.”
It was a flash of unguardedness from the relentlessly on-message Mr. Hawley, the Missouri attorney general, who is seeking the Republican nomination in the state’s Senate race. Riding in the back of an S.U.V. last month, he was responding to criticism raised by both Democrats and Republicans that his swift rise made him a political opportunist who was looking ahead to a Senate bid when he ran for attorney general two years ago.
“That’s a hard no,’’ he said, as he headed to a campaign stop at a factory in Springfield. “It was not anything — no, that was not on the brain.”
It is a sensitive subject for Mr. Hawley, who campaigned for attorney general with a message of disdain for “ladder-climbing politicians.” One campaign ad showed him walking through a forest of ladders with legs scrambling up them while he remained firmly rooted on the ground.
Ten months after he was sworn in, Mr. Hawley announced his Senate candidacy. He was recruited by party leaders who thought his résumé — Stanford and Yale graduate, law professor, father of two — made him the perfect candidate to challenge the incumbent Democrat, Claire McCaskill, for a seat that Republicans believe is one of the most vulnerable in the Senate this year.
And he was backed by a who’s who of the state’s conservative donor class, including former Senator John Danforth, the businessman David Humphreys and the former ambassador Sam Fox.
Mr. Hawley said he decided to enter the race because it was “such an urgent moment for the country.” Since then, he has crisscrossed the state and established himself as the front-runner for the Republican nomination, to be decided in a primary on Aug. 7.
Polls suggest it could be a close race against Ms. McCaskill in November, and Mr. Hawley has opened a new front against her with President Trump’s nomination this week of Judge Brett M. Kavanaugh to the Supreme Court.
Ms. McCaskill opposed the confirmation of Justice Neil M. Gorsuch last year and said on Monday that she would be “thoroughly examining Judge Kavanaugh’s record in the coming weeks.” Mr. Hawley has taken an aggressive stance on the issue, warning voters in an ad campaign that “our way of life is at risk.”
“The eyes of the nation are on Missouri,” Mr. Hawley said in the ad. “Claire McCaskill wants liberals in charge. That’s how she votes. That’s not Missouri’s way, and it won’t be my way.”
In a wide-ranging interview over a day of campaigning, Mr. Hawley rejected criticism that he is a candidate in a hurry, as well as complaints from some in his own party that he has exhibited a sense of entitlement about the nomination by skipping local party dinners and declining to debate his primary opponents.
He said he was surprised when party leaders like Senator Mitch McConnell, the majority leader, and the strategist Karl Rove encouraged him to run.
“I guess I was surprised at the depth of antipathy towards Claire McCaskill and the sense of real urgency folks had,” he said.
He has delivered that message to voters in blunt, sometimes ominous tones. At an event organized by the Missouri Dairy Association, he stood in bluejeans and leather boots before a line of picnic tables and warned a crowd of farmers that Ms. McCaskill was a threat to everything they hold dear.
“Farming is a way of life, it’s a way of life that you live everyday, it’s a way of life that I grew up in, it’s a way of life that is worth preserving, but it’s a way of life that is also under threat,” he told the group.
Mr. Hawley said the threat came from federal bureaucrats, “folks on the coasts” and members of “the D.C. cartel” like Ms. McCaskill. If elected, he said, he would “fight for us and for our way of life.”
Republicans are counting on Mr. Hawley’s record as a vote-getter to propel him to victory in a state that Mr. Trump won by about 19 points.
As a first-time candidate in 2016, he earned more votes than anyone else on the Missouri ballot, including Mr. Trump, Senator Roy Blunt and former Gov. Eric Greitens, who resigned in May amid a series of scandals that had threatened to weigh down Mr. Hawley’s campaign.
“He ran ahead of everybody,” Mr. Danforth said in an interview. He described Mr. Hawley, who wrote a biography of Theodore Roosevelt for Yale University Press at the age of 28, as “a scholar, really.”
“He is very well read,” said Mr. Danforth. “He is not just some glad-handing politician.”
Raised in the small town of Lexington, Mo., Mr. Hawley is a telegenic 38-year-old with impeccable conservative credentials, including leadership of the Federalist Society at Yale Law School, work with a conservative religious liberty group and a clerkship with Chief Justice John Roberts (where he met his wife, Erin, a fellow clerk).
After practicing law in Washington, he returned to his home state and taught constitutional law at the University of Missouri before running for attorney general.
He exudes a friendly enthusiasm, but the timbre of his voice hardens when he talks about “liberals” or “elites.”
“I’m not happy that people in Washington, D.C. — and, let’s be honest, New York, on Wall Street, in Hollywood — look down on the kind of upbringing I had,” Mr. Hawley said.
Mr. Hawley wants Missouri voters to think Ms. McCaskill looks down on them, too. He says she has “sold out the whole Midwest way of life,” a narrative that Ms. McCaskill — who grew up in a small town and waited tables to pay her way through the University of Missouri — rejects.
Meira Bernstein, her spokeswoman, said it was “absurd” to claim that Ms. McCaskill had lost touch with her constituents, including Trump supporters. She said the senator had held town-hall meetings across the state and had voted for about half of Mr. Trump’s cabinet nominees and most of his judicial nominees.
But Ms. McCaskill has made missteps in recent weeks that have highlighted her affluence and helped give traction to Mr. Hawley’s attacks.
Her financial disclosure forms revealed that her husband made between $230,000 and $2.1 million from a $1 million investment in a hedge fund connected to the Cayman Islands, an offshore tax haven, according to McClatchy. Ms. Bernstein declined to comment on the report.
And after announcing a bus tour of the state, Ms. McCaskill used a private plane to travel to some of the stops. Her spokeswoman said she paid for the plane trips herself, but the Hawley campaign has savored the optics of Ms. McCaskill flying from town to town across a state that winces at the term “flyover country.”
Mr. Hawley has hewed closely to the president, who endorsed him last year, saying Mr. Trump was “really doing a great job” and that he disagreed with the president on “nothing that has happened so far.”
That includes contentious issues like the separation of parents and children who cross the United States border illegally. Asked last month about the practice, before Mr. Trump’s order reversing the policy, Mr. Hawley said it was a matter of upholding law and order.
“If people didn’t cross the border illegally this wouldn’t happen,” he said. “It is an entirely preventable tragedy: Don’t cross the border illegally and this won’t happen.”
Mr. Hawley also supports the president’s brass-knuckle approach to international trade, including the imposition of tariffs, a tactic that has produced anxiety in a state where agriculture is a big business.
“I’m willing to give him the benefit of the doubt on it until we see what kind of a deal he gets,” Mr. Hawley said. “I think it is worth it if it works.”
But Mr. Hawley has run into some hurdles that appear to be of his own making.
There have been questions about how he spends his time. His official calendar as attorney general contains long stretches that are unaccounted for, according to a New York Times review of his calendar documents from 2017 and 2018 obtained through a public records request. Local media outlets have also published pictures of him buying wine or lifting weights at a gym far from the office in the middle of the work day.
His aides say his calendar is left incomplete as a way to protect sensitive legal information. And they note that Mr. Hawley has intensified his campaign schedule, traveling across the state in recent weeks.
Mr. Hawley has also ruffled some feathers in his own party, angering conservatives by calling for Mr. Greitens to resign after allegations of sexual misconduct emerged.
Dean Moore, the chairman of the Christian County Republican Central Committee, outside Springfield, said he had heard “resentment toward people who get into an office and immediately look for another office.”
“It’s nothing personal against Josh Hawley,” he said. “He probably would make a great senator, but we would just prefer the establishment handle things like that differently instead of grooming people to be their next favorite.”
But not everyone at the grass roots level agrees. David Zucker, the party chairman in St. Charles County, outside St. Louis, encouraged Republicans to “keep your eye on the prize.”
“He didn’t come to your dinner. So does that mean Claire McCaskill gets six more years?” he said. “She didn’t come to your dinner, either!”