For the first time in more than 40 years, a Republican could win the governor’s seat in Oregon, breaching the seemingly solid Democratic line of states running along the Pacific coastline of the US.

The tight race between former Oregon House speaker Tina Kotek, a Democrat, and former Oregon House minority leader Christine Drazan, a Republican, which in the latest polling showed Drazan with a hairline lead, indicates a rebuff of the current term-limited liberal governor, Kate Brown.

Brown has one of the lowest approval ratings of any governor in the country amid brewing concern over how state leadership has handled everything from the pandemic to homelessness.

But it’s a third-party candidate with support from both Republicans and Democrats, along with contributions from the richest man in the state, that have truly set a Republican on a path toward possible victory.

“Democrats are pretty good at running a red-blue race in Oregon … But the dynamics of a three-way race have really kind of thrown that playbook out the window,” said Jake Weigler, a progressive political strategist in Oregon not involved in the race.

Betsy Johnson, who was a moderate Democrat while serving as a state senator and now is running as an independent, has been forecast to receive as much as 14% of the vote. Outside of independent voters, 17% of Democrats plan to vote for her, while only 9% of Republicans do, according to an Emerson College Polling survey released earlier this month.

Rebecca Tweed, a Republican strategist in Oregon with no connection to the governor’s race, said it will be this subset of voters to watch come election day.

“We’ll have to see if any of those voters that got pulled toward Betsy end up going back into their corners of the Democratic and Republican parties,” she said.

But it could also come down to what independent voters decide to do next month.

Ariya Ahrary, who has lived in Oregon since 2007, said she was initially very happy to see the independent candidate on the ballot. But after taking a closer look at each candidate’s policies, she said she now will likely vote for Kotek in hopes that she will help change the direction of the state.

“We do want actual real change instead of just all talk. Hopefully that happens, that it’s not just all talk, that it’s actual action,” she said.

By far Johnson’s largest single financial contribution has come from Phil Knight, co-founder of Nike. Altogether, he has sent $3.75m to Johnson’s campaign since January, and then earlier this month sent $1.5m to Drazan. In an interview with the New York Times earlier this month, he said he would do anything to keep Kotek out of the governor’s seat.

The gubernatorial race projections in a state where Joe Biden won by 16 points just two years ago have been a shock to many across the nation. They have prompted national political figures to visit the Pacific north-west hoping to drum up support for their candidates.

On Saturday, Biden spoke at an event in Portland, where he highlighted the increasingly important role governors play in policy implementation, while praising Kotek’s leadership and bravery.

“You’re a progressive state. You’re a state that’s always been ahead of the curve. Stay ahead of the curve, and elect Tina,” he said.

Virginia governor Glenn Youngkin, a rising Republican star, spoke at a rally for Drazan on Tuesday, while Senator Elizabeth Warren, a Democrat from Massachusetts, attended an event for Kotek this weekend.

Kotek, Drazan and Johnson recently came together for the race’s final televised debate. The largely mild-mannered occasion was punctuated by sharp criticisms hurled between Drazan, Johnson and their Democratic rival, including over abortion.

Following the US supreme court’s overturning of Roe v Wade earlier this year, Oregon has positioned itself as a safe haven for abortions. Johnson, a former Planned Parenthood board member, described herself as pro-choice. Kotek, who was endorsed by Planned Parenthood PAC of Oregon and helped with the legislative effort to codify abortion access into state law in 2017, said she is a strong supporter of abortion access, including potentially using taxpayer money to support that type of care. She accused Drazan of posing a threat to abortion access in the state.

Drazan rebutted by saying while she wouldn’t use taxpayer funds to support abortion, the practice would remain legal. “It gets more and more startling to me the extent to which Tina Kotek will lie to voters,” she said

Another key issue the candidates responded to during the debate was the state’s response to the pandemic when it came to closing schools. Drazan accused both Governor Brown and Kotek of throwing “our kids under the bus”, while Johnson said: “The single worst thing we did during Covid was to shut kids out of the classroom.”

Kotek, who agreed that students were kept out of the classroom too long, said it was in fact her Republican opponent who did the throwing by voting against a multibillion-dollar education bill in 2019.

But it was a question from a resident of Wilsonville, a city about 17 miles south of Portland, that spotlighted an issue at the center of this race: “Since you’ve been a lifelong Democrat, how do you square yourself with knowing that your current efforts will probably cost Democrats the governorship for the state?”

Johnson told the audience that she joined the race because she sees herself as the best candidate to lead a state that has “gone off the rails”, and that she has no plan to drop out.

She said: “I believe sports oddsmakers don’t win games. Polls don’t predict elections. I’ve seen enough fourth-quarter finishes to know that it’s not over until it’s over. And I’m in this race until the absolute end.”