TONGANOXIE, Kan. — In any other year, Rep. Roger Marshall would have been a slam dunk to fill this state's open Senate seat, held by Republicans since 1932.

Marshall, 60, is an obstetrician, the first in his family to go to college and a military veteran who served seven years as a captain in the Army Reserve. He espouses the antiabortion, fiscally conservative views that appeal to many in this mostly red Midwestern state, and he survived a tough primary challenge by a well-known conservative in August.

Before the coronavirus pandemic, there was little hope for Democrats to turn blue the open seat vacated by the retiring Sen. Pat Roberts. But the resulting health crisis and recession, as well as left-leaning anger about Republicans’ attempt to push through a Supreme Court nominee days before an election, has made this once sleepy race a close contest.

Marshall’s Democratic opponent, Barbara Bollier, 62, a state senator who only recently left the Republican Party, is also a physician and has centered her platform on pandemic response and expanding health care for needy Kansans. She has racked up a record third-quarter fundraising haul of $13.5 million and has raised a total of $20 million. Marshall raised $2.7 million in the third quarter and has a total of $5 million.

Marshall is still favored to win — the Cook Political Report, a nonpartisan tip sheet, has continued to rate the contest as “leaning” Republican — but internal polls on both sides show a tight race.

At a recent rally on a brilliant fall day in the northeastern part of the state, Marshall and his bright red “Keep Kansas Great” bus stopped for a rally at a park next to a Veterans of Foreign Wars post. He was introduced by Kansas royalty — Mary Jean Eisenhower, a granddaughter of President Dwight D. Eisenhower — who lauded Marshall’s volunteer work treating coronavirus patients early in the pandemic.

Control of the Senate was top of mind. In his remarks, Marshall soberly told the crowd that “if we lose the Senate majority . . . the history of America will be forever changed.”

Judy Glenn, 65, an avid supporter of President Trump and a retired country music promoter, buttonholed Marshall after he spoke to make sure his support of Trump would be absolute.

“I wanted to make sure he’s going to go and back our president,” she said. “That’s what I vote for.”

Marshall, a two-term congressman from the sweeping western part of the state, has campaigned heavily on his close association with Trump, with an early primary ad proudly touting his record of voting “98 percent” with the president and concluding with the slogan “Trusted by Trump.” In a state Trump won by more than 20 percentage points in 2016, that still goes over well with some conservative voters.

Yet Kansas, reliably red in presidential elections, has an avowed centrist streak, voting for Democratic governors such as Laura Kelly, the current chief executive, and moderate Republicans such as former senator Nancy Landon Kassebaum. (Kassebaum has endorsed Bollier, while the state’s other Republican Senate eminence, Robert J. Dole, has endorsed Marshall.) But the suburbs of Kansas City have been trending blue in recent years — Democrats elected Sharice Davids, a Native American lesbian, to Congress in 2018 — and that trend is likely to hold in 2020, analysts say.

Trump has been less popular here than in red states such as Kentucky, Missouri and South Carolina, said Patrick Miller, a political science professor at the University of Kansas.

“We’re still a red state, but we’re pinker than people think we are,” he said.

The Republican establishment breathed a sigh of relief in August when Marshall emerged victorious after a crowded primary that included a challenge from Kris Kobach, a polarizing former Kansas secretary of state who long espoused hard-line views about immigration and voter rights.

Conventional wisdom at the time posited that Bollier’s best chance of winning the seat would be if she faced Kobach in the general election because he was widely considered a poor campaigner who lost to Kelly in the state’s gubernatorial contest in 2018. Outside money poured in, with a Democratic super PAC spending more than $5 million to boost Kobach, according to an analysis by the Center for Responsive Politics.

Marshall was the second choice of Senate Majority Leader Mitch McConnell (R-Ky.), who had urged Secretary of State Mike Pompeo to join the race. When Pompeo decided against it, McConnell shifted his support — and PAC money — to Marshall, with the McConnell-aligned Senate Leadership Fund spending more than $12 million. Democratic-affiliated Duty & Country is set to spend $7.5 million, Politico first reported.

On the stump, Marshall has continued to assert his conservative bona fides, criticizing ­Bollier’s positions on abortion — she supports abortion rights — and gun control, alleging in a recent debate that she “just doesn’t represent Kansas values.” Republicans have criticized her as an out-of-touch “extreme liberal” who hails from a tony mansion-dotted neighborhood in Kansas City, rather than Marshall’s hometown in the rugged plains.

Bollier, on the other hand, has tried to present herself as a moderate who can work with both sides of the aisle, while emphasizing her roots as a centrist Republican who split with her party in 2018 when it added an anti-transgender-rights plank to the state party platform.

“That was the last straw,” ­Bollier said in an interview. “I had been at odds with the Republican leadership for years on school funding and expanding Medicaid. At some point, you have to recognize you can’t participate in a party that continues to block what you need to do to get your work done.”

Republicans argue that in a state where the GOP has a 2-to-1 advantage, the numbers are in their favor.

“Kansans, and Kansas Republicans in particular, are more traditional and private about their vote,” said CJ Grover, a spokesman for the Kansas GOP. “It’s why you generally see high numbers of ‘undecided’ voters showing up in polling but double-digit victories for GOP candidates on Election Day. So a race perceived as neck and neck in the low 40s based on polling likely foretells a double-digit, or close to it, win for Roger Marshall.”

But privately, Republicans worry about Bollier’s cash advantage and polls that, although still within the margin of error, show a tight race.

“It’s not a fair fight right now,” said a state Republican operative who spoke on the condition of anonymity to be frank about the race. The operative said Bollier was benefiting from “the environment and the passion of the other side and the tremendous amount of money that’s flowed to it.”

In addition, the operative noted, the national GOP flooded the state with help and workers in 2014 when Roberts was in a tight race. None of that is happening now, the operative said, an indication that the Republican Party is stretched thin with more high-profile Senate battles in states such as Iowa and North and South Carolina.

Until recently, the two candidates have run divergent campaigns, with Marshall doing traditional meet-and-greets with voters and Bollier running a virtual race.

Health care has been a central issue between the two doctors: Bollier supports expanding Medicaid for low-income residents — Kansas is one of 12 states without the expansion — and Marshall opposes it, saying it is too costly. Marshall’s former ownership of a for-profit hospital also has come under fire; one attack ad noted its rise forced a nonprofit hospital in the same town to limit services.

A Kansas City Star investigation this week suggested that Marshall pushed for Congress to overturn restrictions on physician-owned hospitals while his wife, Laina, profited personally from them.

Eric Pahls, Marshall’s spokesman, did not return telephone calls or emails for comment.

Bollier has been critical in the debates and on the stump of Marshall’s support of Trump’s handling of the coronavirus pandemic. Marshall gave the president an “A+” for his response to the crisis and at one point announced that he had put his family on hydroxychloroquine, an anti-malarial drug Trump claimed could benefit those sickened by the virus despite a lack of clear evidence.

“Leaders need to lead, particularly physicians,” Bollier said. “Kansas is exploding right now with COVID cases. We’re hot red. We need to take this seriously.”

Lately, Bollier has ventured out to “lawn chair chats” with constituents social distancing in parks across Kansas. At one recent event in Topeka, she seemed giddy when she described polls the campaign has said are turning her way.

“How is this race going?” she said. “Oh my gosh, I’m so excited. . . . Momentum is on our side.”

Connie Carson, 77, a retired elementary school teacher who came to hear Bollier speak, said she would be voting for her.

“We’re worried about health care and we’re worried about the virus,” she said. “Bollier has a much more intellectual, practical side of taking care of it. For Marshall, when Trump says jump, he says, ‘How high?’ Even though he’s a doctor, I don’t think he has a realization of what it’s going to do to take care of this virus. It’s not going to be easy.”

Russell Arben Fox, a political science professor at Friends University in Wichita, said that Bollier is running a “smart campaign” at a time when Trump is driving moderate Republicans and independents away from the party. He noted in particular her campaign ads that stress her support from Republican legislators, including a recent one with a Flint Hills rancher and State Rep. Larry Hibbard, who said he supports Trump but will be voting for Bollier.

“Maybe she’ll pull it off, but I probably wouldn’t put money on it,” Fox said. “It’s certainly a tighter Senate race than has happened in Kansas in years.”

Julie Tate and Emily Guskin contributed to this report.