(The Hill) – Hard-right candidate Kathy Barnette has come from nowhere to make the Republican Senate primary in Pennsylvania one of the tightest and most interesting races in the country.

Barnette, a conservative commentator, is gaining fast on two candidates who have vastly outspent her: TV personality Mehmet Oz, who is backed by former President Trump, and businessman David McCormick

Barnette was in fifth place and in single digits in the RealClearPolitics polling average just last month. She’s now polling around 20 percent in the multicandidate race, on a near par with Oz and McCormick. A Barnette victory in Tuesday’s primary is very plausible.

“It’s nip and tuck right now,” said Terry Madonna, a senior fellow in residence for political affairs at Millersville University and a longtime expert on polling and Pennsylvania politics. “It’s a real three-way race.”

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Barnette’s rise has set alarm bells ringing across a swath of the political spectrum, however. 

Her polling climb concerns moderate Republicans who fear she is unelectable in a general election, prominent backers of Trump who think she might thwart Oz and centrists who fret she is another emblem of the nation’s accelerating polarization.

The only two camps that are happy are Barnette and her backers, now including the well-financed Club for Growth, and Democrats who think she might be the most beatable of the three leading Republican candidates.

A Thursday report from CNN’s “K-File” team unearthed old comments from Barnette in which she described gay men as “not normal,” suggested same-sex marriage would ultimately lead to widespread acceptance of pedophilia and falsely asserted that former President Obama is a Muslim.

In an interview, NBC News reporter Dasha Burns confronted Barnette with an old tweet in which the candidate said pedophilia was “a cornerstone” of Islam. 

“I don’t think that’s me. I would never have said that,” Barnette replied. 

More generally, the candidate complained that “it’s very unfair to take a snippet” of old comments.

Barnette is getting pushback from her GOP opponents in the final days before the primary. 

McCormick, for example, noted that she lost a House election in 2020 by almost 20 points. A Trump statement asserted that she “will never be able to win the General Election against the Radical Left Democrats.”

But Barnette has risen fast by stoking some of the same passions as Trump around inflammatory social issues. In her case, that rhetoric is allied with a personal story of growing up in poverty in Alabama and empathy with voters who are feeling financially pinched.

Even observers who share none of her politics see why she has climbed in the polls.

“For Dr. Oz and McCormick, any rational observer would agree they are outside their comfort level and pandering to the far right,” said former Rep. Jason Altmire (D-Pa.), who served three terms as a moderate congressman and later wrote a book lamenting the erosion of the political middle ground.

“That has opened the door for this third candidate, Kathy Barnette — and she is a true believer. She is in no way outside her comfort level. It is completely in her wheelhouse,” he added.

Madonna, the academic expert, added that Barnette has benefited from a close, if informal, alliance with gubernatorial candidate Doug Mastriano, who is cut from similar cloth. 

Mastriano, a state senator, pushes false claims of fraud in the 2020 election and was present near the U.S. Capitol on the day of the Jan. 6, 2021, insurrection.

“They even have their campaign signs attached side by side,” said Madonna. “She has risen because she has picked up the Mastriano base of very loyal Trump supporters.”

Some Republicans fear that a win for Barnette could give Democrats a fighting chance of gaining a Senate seat, which could be vital given the current 50-50 makeup of the upper chamber. 

Oz, McCormick and Barnette are seeking to replace retiring Sen. Pat Toomey (R-Pa). John Fetterman, a progressive Democrat and Pennsylvania’s current lieutenant governor, is the strong favorite to win his party’s primary.

Barnette looks to be exactly the kind of candidate Senate Minority Leader Mitch McConnell (R-Ky.) was warning about last month.

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“You can’t nominate somebody who is just sort of unacceptable to a broader group of people and win,” McConnell said. “We had that experience in 2010 and 2012.”

McConnell was referring to past election cycles in which Republicans lost winnable Senate elections with nominees such as Delaware’s Christine O’Donnell, who had to emphasize in one campaign ad that “I am not a witch,” and Missouri’s Todd Akin, who mused that women would usually not become pregnant in instances of “legitimate rape.”

In the past, “Republicans have left too many Senate seats on the table,” said Doug Heye, a former communications director of the Republican National Committee. 

Heye added that Barnette had “come up so fast” that she had apparently evaded vetting until the last moment. Expressing concern about her tweets, he added, “I just don’t know how much is there because it’s so new.”

He also noted that there were other concerning races for the GOP, including the Missouri Senate primary in which former Gov. Eric Greitens has a polling lead. Greitens has been accused of abuse by his ex-wife and of sexual misconduct by a former lover. He denies those allegations.

“It’s not necessarily that Greitens is unelectable, but he certainly could be,” said Heye. “Greitens is the only one who could lose.”

There are months to go before the Missouri primary, however. 

By contrast, Pennsylvania GOP voters will deliver their verdict on Tuesday — and the political world will take note of what they say.

The Memo is a reported column by Niall Stanage.