Pennsylvania’s Republican Senate primary is in chaos.

Kathy Barnette’s late surge has turned the nationally watched race into a mad scramble, with former President Donald Trump warning Republicans against nominating her and opponents only now doing basic background research in an attempt to stop her as the clock ticks closer to Tuesday’s primary.

Such vetting, usually strategically unspooled over the course of a lengthy campaign, rolled out in frenetic bursts at a range of disparate targets Thursday.

The rush to find anything to puncture Barnette’s story came as she threatened to overtake longtime GOP front-runners Mehmet Oz and David McCormick, who have spent tens of millions of dollars on the campaign but failed to pull away.

The haphazard moment was embodied by a Trump statement urging Republicans to support his endorsed candidate, Oz, but also predicted a bright future for Barnette, a conservative commentator and a prominent election denier with a trail of incendiary comments, including some targeting gay and transgender people and Muslims.

“Kathy Barnette will never be able to win the General Election against the Radical Left Democrats,” Trump said.

“She has many things in her past which have not been properly explained or vetted,” he added, “but if she is able to do so, she will have a wonderful future in the Republican Party — and I will be behind her all the way.”

» READ MORE: How Kathy Barnette’s election denial helped her become a GOP front-runner in the Pa. Senate race

Barnette, 50, brushed off the attack during a campaign stop Thursday night at the Southampton Fire Department in Bucks County.

“We know that President Trump did not mince words,” she told reporters after the event, though media were largely barred while it took place. “I think that letter was favorable. And I look forward to working with the president.”

She agreed with a suggestion that being targeted was confirmation of her rise.

“There’s a reason we have the words swamp creatures,” she had told the crowd earlier, according to a recording made by reporters who were briefly inside but forced to leave. ”The long knives are coming out at this point, and I had the best day of my life today.”

Barnette responded to questions about her background in a 25-minute interview with conservative radio host Chris Stigall. She accused her opponents, and some conservative media figures, of twisting past statements.

She explained her work history, where she went to college, when she moved to Pennsylvania (2014, according to a GOP questionnaire she once filled out), and her 10 years in the Army Reserve. She described her political fight now as “David and Goliath.”

Barnette’s campaign had spent less than $2 million as of April 27, according to public disclosures. That’s dwarfed by more than $35 million from McCormick and two super PACs funded by his wealthy allies, and more than $18 million by Oz and his supporters.

As rivals raised questions about her chances of winning a statewide election, Barnette noted that Oz and McCormick have already bloodied each other with brutal ad campaigns.

“Why would you take people with very high negatives in the Republican primary into the general [election] and think you’re gonna win?” she asked in the radio interview.

Barnette, running a tireless race on a shoestring budget, has stunned insiders in both parties. She has capitalized on Oz and McCormick’s withering attacks on each other, her own combative rhetoric, and her ties to State Sen. Doug Mastriano (R., Franklin), the leading GOP candidate for governor.

But her prominence, like Mastriano’s, has some Republicans worried they could nominate a pair of candidates too extreme to win a swing state, even in a year that appears likely to strongly favor the GOP.

”I have concerns about some of the things I’ve heard her say, and I think it’s incredibly important that the person that’s nominated can win this seat,” McCormick, an Army veteran and former hedge fund CEO, said during a campaign stop in Northeast Philadelphia. “We have to have someone who can withstand what’s going to be required in the general election to win.”

Strategists were wrestling with whom Barnette might weaken more, Oz or McCormick, if she can’t win — illustrating how she had upended a contest focused for months on just two contenders.

Barnette, with her combative style and history of challenging the 2020 election, has many qualities that appeal to Trump’s supporters.

But some Republicans worry about past comments attacking gay people and Islam. She once called the religion “a political and a military system that is incongruent with the U.S. Constitution,” CNN reported, and tied it to pedophilia. On her radio show in 2015, she said, “Two men holding hands, two men caressing, that is not normal,” the cable news outlet reported.

She also embarked on a failed push to find voter fraud after losing a 2020 U.S. House race. But neither Republicans nor Democrats took her seriously enough to dig through her history or personal story until now.

This late in the race, it’s unclear if the attacks will have enough time to sink in before Tuesday’s vote, though a super PAC aligned with Oz blasted them out by text message Wednesday and Thursday.

» READ MORE: Kathy Barnette is the surprise Pa. Senate candidate who just might win. Now she’s getting new scrutiny.

After McCormick allies earlier this week challenged Barnette to produce records from her decade in the Army Reserve — which she did — her rivals turned to other topics Thursday. A McCormick aide pointed out Barnette said she worked “on Wall Street,” but an old LinkedIn profile listed her working in St. Louis for Bank of America’s investing arm.

Others accused Barnette, who is Black, of expressing sympathy for the Black Lives Matter movement because she tweeted the #BLM hashtag.

Yet that led to a video in which she sharply criticized violence that followed some protests after the 2020 police murder of George Floyd. Barnette told Stigall she only used the hashtag to inject her views into the online discourse.

Oz, appearing on Fox Business, said Barnette “attacked George Washington.”

It was a reference to a 2019 YouTube video in which Barnette, while visiting Washington’s Mount Vernon home, discussed the people he enslaved, praising their strength and perseverance and saying Black people should honor what they endured. She said that while some white visitors saw Washington as “high and mighty,” Americans should have a “balanced” view of the country’s history, good and bad.

“The best way we can honor those slaves who came before us as Black people is to live an honorable life,” she said in the video.

Oz also questioned whether she could win a key swing state.

“She said things that are going to make her very difficult to elect in a general election,” he said on Fox Business. “The Republican community’s going to coalesce around me. I’m confident in part because of [her] past statements, in part because of the clear mission and vision we’ve been offering to the voters of Pennsylvania.”

His appearance came a day after Fox News host Sean Hannity, who has endorsed Oz, hammered Barnette in a 10-minute segment.

Hannity slammed Barnette for old social media posts in which she appeared to criticize Trump and support a statue of Barack Obama. In the posts, allegedly from Barnette’s Twitter account but no longer available, she criticized a Trump debate performance during the 2016 Republican presidential primary, calling it “horrid,” and saying he was “just as liberal as” Democratic leaders.

She made other critical statements about Trump that year, like many Republicans, but by the spring was posting feverishly in his favor.

Barnette told Stigall she voted for Trump in both the 2016 primary and general elections. And she said she called for an Obama statue because she wanted more statues at a time when activists were removing some recognizing Confederate figures, and thought it would be appropriate to honor the country’s first Black president.

» READ MORE: Get to know the 2022 candidates for Pa. Senate and governor

Outside Barnette’s event Thursday night, Rich Hohenshilt said the new attacks don’t change his plans to vote for her, but he does want to know if there’s anything that could be unearthed later.

”They’re gonna throw everything at her including the kitchen sink,” said Hohenshilt, 55, a cross-country truck driver from Penndel who wore a Trump hat and Barnette T-shirt. “They’re gonna do every lie that they could possibly do. … They’re gonna do everything they can to knock her out.”

He also said he loves Trump, but “Donald Trump is not Jesus. He’s capable of making a mistake, and she believes he made a mistake by endorsing the wrong person. And I do, too.”

Barnette also found some defenders in the conservative media, many of whom have also balked at Trump’s Oz endorsement.

On Trump ally Steve Bannon’s talk show Thursday, guest Jack Posobiec said that what opponents are doing to Barnette “is the same thing they did to Donald Trump.”

“They’re going into videos and clipping things completely out of context,” said Posobiec, a pro-Trump commentator prominent on social media. “It reeks of desperation to be attacking someone’s military record when you have a woman like her who stepped up and served.”

-Staff writer Anna Orso contributed to this article.