Influential Republicans in Washington and among the nationwide party elite are having a belated "oh s--t" moment over the previously unimaginable prospect that Kathy Barnette could win their party's nomination for the open Senate seat in Pennsylvania.

Why it matters: In Barnette, who's been soaring in the polls ahead of Tuesday's primary, Senate Minority Leader Mitch McConnell would be dealing with a general election candidate who'd be an opposition researcher's dream — potentially endangering the GOP effort to take back the Senate.

• McConnell has been fixated on ensuring the 2022 midterms are not a repeat of the 2012 or 2010 cycles.
• The Kentuckian said Republicans missed good chances to win the majority in those years because they nominated candidates who talked about things like "legitimate rape" or had to publicly assure voters they weren't witches.
• Barnette’s campaign did not immediately respond to a request for comment.

Barnette has surged after releasing a powerful video — "It wasn't a choice. It was a life." — in which she movingly talks about how her mother was raped when she was 11 and yet Barnette is the living, breathing byproduct of that horrific circumstance.

• The video's hit a nerve with primary voters in Pennsylvania, a source close to one of Barnette's rivals told Axios, and gained resonance following the leak of a draft Supreme Court decision that would overturn Roe v. Wade.
• Barnette is also the uncommon Black Republican candidate.

At the same time, a cursory review of her Twitter account, @Kathy4Truth, turned up tweets like this one: "Just confronted a Muslim today."

• She joins Missouri Senate candidate Eric Greitens — whose alleged misdeeds are numerous and graphic — on a list of potential Republican Senate nominees giving heartburn to GOP leadership.
• They not only create the potential of blowing winnable seats but being unmanageable for McConnell should he return as Senate majority leader next year.

Between the lines: The past few days have brought a wild scramble to destroy Barnette. Republican operatives were late to awaken to her political chances.

Most had pegged Pennsylvania's Senate race as a two-man battle between celebrity TV doctor Mehmet Oz and former hedge fund CEO and Army veteran David McCormick.

• Oz and McCormick — and their outside operations — have spent millions nuking each other with vicious commercials saturating Pennsylvania television.
• Oz has attacked McCormick as soft on China, and McCormick has hit Oz for his past comments that are supportive of abortion and gun control.
• That two-man ad war has hurt both candidates and provided a rare opportunity for Barnette to sneak up, ignored and untouched.
• Neither rival nor their backers have put serious money on TV to promote her history of comments that would ordinarily disqualify a candidate in a general election, if not a Republican primary.

As Oz and McCormick blitzed each other — and as former President Trump endorsed Oz and blasted McCormick — Barnette has glided through the carnage.

• She's had virtually no money but gotten traction with the GOP base by relentlessly hyping Trump's false claims of a stolen 2020 election.

Trump ally Steve Bannon described Barnette as an "audience favorite" for his "War Room" podcast, which is popular among the MAGA base.

He's praised her for having never stopped talking about decertifying the 2020 Biden election and for refusing to concede her own loss in a 2020 House race.

• "The reason she has struck a chord is she NEVER conceded her House race loss," Bannon told Axios in a text message. "Pennsylvania is MAGA v. ULTRA MAGA."
• Barnette's also close to the pillow entrepreneur and "Stop the Steal" leader Mike Lindell. And she's effectively running on a ticket with the leading Pennsylvania gubernatorial candidate, state Sen. Doug Mastriano.
• He went to the Capitol on Jan. 6 and has been subpoenaed by the investigative committee. (Mastriano says he left before the building was breached.)

A Barnette nomination next week would present a lose-lose for Republican leadership.

• Worst case: She proves to be as big a liability as many fear and hands a competitive seat to the Democrats.
• Best case: She's elected and ends up a thorn in the side of Senate leadership. She's already signaled hesitancy about backing McConnell as the Republican leader.
• That potentially aligns her with candidates such as Greitens, who's said he won't back McConnell. The Greitens campaign says its internal polling has him leading his primary contest, despite potentially catastrophic general-election baggage.

What's next: Prominent Republicans are belatedly trying to kill Barnette's momentum.

Ric Grenell, a Trump ally who's also endorsed Oz, has been spreading around a video of Barnette's past comments about "white racism."

• GOP operatives have been passing around negative articles about her from Breitbart and the Washington Examiner.
• Pat Toomey, the Republican senator vacating the Pennsylvania seat, told Axios: "There's a lot ... voters don't know about her. A lot."

On Wednesday, one Republican operative aligned with a rival campaign reached out to Axios to flag Barnette's comments regarding systemic racism in the U.S. and the country's complicated history of racial discrimination and slavery.

• The calculation, the operative conceded, is to damage Barnette among Republican base voters presumed to be hostile to ostensibly progressive views about racial justice issues.
• The person also flagged an online petition Barnette created to build a statue in Washington, D.C., honoring Barack Obama and his family.

Nonetheless, it's awfully late in the game for Republicans to destroy Barnette.

• Some heavy hitters also appear to be staying on the sidelines.
• One group with a massive bank account and the potential to affect GOP races — the McConnell-allied Senate Leadership Fund — has no plans to engage in the Pennsylvania primary, a source with direct knowledge of the group's plans told Axios on Wednesday.
• Senate Minority Whip John Thune, asked if the establishment is putting its thumb on the scale in the Pennsylvania Senate race, told Axios, "In this case, no, we're not. ... We're going to let the voters vote their will" — although he added he hasn't been paying close attention to the race.

Barnette has built up impressive momentum in recent weeks.

She's surged in the polls from mid-single digits as recently as April to around 20% now.

Multiple attendees of a Trump-Oz rally last weekend said they're backing Barnette.

• At the same time, a cavalry of sorts is finally coming to Barnette's aid.
• The well-funded conservative group, the Club for Growth, shocked Barnette's competitors when it booked $2 million worth of TV ads on Tuesday in support of her.
• The New York Times reported that Club for Growth expenditure is more than 10 times the total Barnette's campaign itself had spent on TV to date.
• The powerful anti-abortion group Susan B. Anthony List, the Republicans' answer to the pro-choice group Emily's List and a powerful player in GOP primaries, endorsed Barnette, as well.