With the hours winding down until Tuesday’s primary in Pennsylvania, Republican candidate Dave McCormick was making a final pitch to voters.

"I believe I'd be a great senator fighting for you," McCormick told supporters on Monday morning, in the first of three primary eve campaign events across the Keystone State. "I need you to go tell 10 people… this is so important. This is the most important race in your lifetime."

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For the past couple of months McCormick, a former hedge fund executive, West Point graduate, Gulf War combat veteran and Treasury Department official in former President George W. Bush's administration, was one of the twin front-runners in the race for the GOP Senate nomination in the race to succeed retiring Republican Sen. Pat Toomey, along with Dr. Mehmet Oz, the cardiac surgeon, author and well-known celebrity physician who until the launch of his Senate campaign late last year was host of TV’s popular "Dr. Oz Show."

Dave McCormick campaigns

Republican Senate candidate Dave McCormick speaks with supporters on the eve of the Pennsylvania primary at a campaign event in Middletown, Pennsylvania, on May 16, 2022. (Fox News )

But in recent weeks veteran and conservative political commentator Kathy Barnette has surged in public opinion surveys, turning into a three-way clash the Republican primary in the Senate race in a crucial battleground state that could decide whether the GOP wins back the Senate in November’s midterm elections. 

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Among those recent surveys was a Fox News poll conducted May 3-7 and released last week that indicated Oz at 22%, McCormick at 20%, Barnette at 19%, with 19% supporting other candidates and 18% still undecided. 

Since her surge in the polls, Barnette has faced constant incoming fire from her rivals and other Republicans, concerned over her lack of vetting and past controversial comments and worries that she’s too extreme to win a statewide general election in a purple state like Pennsylvania.

Kathy Barnette campaigns

Republican Senate candidate Kathy Barnette campaigns in West Chester, Pennsylvania on May 13, 2022. (Fox News )

"Everybody is coming after me," Barnette said on the campaign trail Saturday in West Chester, Pennsylvania. "Why do you think that is? Because I’m winning and that’s a problem."

One of those speaking out is former President Donald Trump, who's backing Oz and held a rally in Pennsylvania with Oz a week and a half ago.

TRUMP TAKES AIM AT BARNETTE IN PENNSYLVANIA GOP SENATE CLASH

"Kathy Barnette will never be able to win the General Election against the Radical Left Democrats," the former president – who 16 months removed from the White House remains the most popular and influential politician in the GOP, said on social media on Thursday. "She has many things in her past which have not been properly explained or vetted."

Pennsylvania Senate candidate Mehmet Oz, left, accompanied by former President Donald Trump speaks at a campaign rally in Greensburg, Pa., Friday, May 6, 2022. (AP Photo/Gene J. Puskar)

Pennsylvania Senate candidate Mehmet Oz, left, accompanied by former President Donald Trump speaks at a campaign rally in Greensburg, Pa., Friday, May 6, 2022. (AP Photo/Gene J. Puskar) (AP Photo/Gene J. Puskar)

Oz has repeatedly taken aim at Barnette over the past week, saying on Fox News’ "Special Report" on Thursday that "she’s raised questions in her own candidacy that she’s refused to answer." And pointing to her 2020 congressional loss, Oz emphasized that "this is a candidate who lost by 20 points when she ran for Congress 18 months ago, so she’s not going to do well in the general election."

And Oz told Fox News' Rich Edson over the weekend that "Barnette has tweeted some reprehensible messages, Islamophobic, homophobic…Now she has to own those messages and explain lots more about what’s going on with her campaign."

In the spotlight, Barnette’s tweet from 2014 that "if you love freedom, Islam must NOT be allowed to thrive under ANY condition," and a tweet from 2016 that [then-President Barack] "Obama is a MUSLIM doing Muslim like THINGS!"  

Oz, who is Muslim, argued that Barnette should be disqualified over those tweets and another from 2015 in which she stated "pedophilia" was a fundamental tenet of the Islamic religion. 

Pennsylvania GOP Senate candidate Dr. Mehmet Oz speaks during a Republican leadership forum at Newtown Athletic Club on May 11, 2022 in Newtown, Pennsylvania.  ((Photo by Michael M. Santiago/Getty Images))

Barnette responded on "Fox News Sunday," saying that "the overwhelming majority of the tweets that are now being presented are not even full thoughts. They’re not even full sentences and yet people take it and begin to build their own narrative around it."

She acknowledged that "I can’t provide a lot of context because again, that’s almost 10 years ago. That’s how far they have to go back and try to find anything on me," Barnette told Fox News host Shannon Bream. "Though I can’t provide a lot of context to that because it’s a half thought and everything is not there for me to be able to speak to it, what I can say is that I love my country and I have always loved my country."

Barnett has also faced intense questioning over her resume, including criticism that official forms don’t back up her claims she served 10 years in the military. "I have never embellished on my record on my time in the military," Barnette responded on "Fox News Sunday."

McCormick, in an interview Monday morning with Fox News Digital, emphasized "I believe I can win the general [election]. I think she [Barnette] would have a much tougher time winning the general."

But he vowed that win or lose on Tuesday, "The stakes are so high. I will back the Republican nominee. The alternative of John Fetterman [Democratic Senate front-runner] and the socialist agenda for our county, would be terrible."

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Barnette has a compelling story that seems to be connecting with voters. She spotlights that she grew up "on a pig farm in Alabama. No insulation. No running water." And Barnette, the daughter of a single mother, revealed at a recent debate that she was conceived in rape.

Also helping Barnette may be that she and state Sen. Doug Mastriano, the front-runner for Pennsylvania's GOP gubernatorial nomination, endorsed each other and have joined forces on the campaign trail. Reporters were prevented from attending a joint Mastriano-Barnette event Saturday in Bucks County, Pennsylvania.

(Fox News )

Mastriano aimed to try and help overturn Trump's 2020 loss to now President Biden, and was at the U.S. Capitol when it was stormed on Jan. 6, 2021, by right-wing extremists aiming to disrupt congressional certification of Biden's Electoral College victory.

Barnette has supported Trump's unproven claims that the 2020 election was "stolen" due to "massive voter fraud." And she agrees with the former president's efforts to repeatedly re-litigate his election loss.

The Oz and McCormick campaigns and outside super PACs backing the two contenders since the beginning of the year have spent tens of millions of dollars to run TV, digital and radio ads attacking each other over their conservative credentials and over key issues since the beginning of the year. 

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McCormick has slammed Oz as a "RINO" (Republican in name only) and is spotlighting comments Oz made in 2019 when he said he had concerns over an Alabama measure that would have led to a near total ban on abortion. And McCormick’s questioned Oz – who holds duel citizenship with Turkey – over his connections to the Turkish government. Oz has repeatedly attacked McCormick for investments in China made by the hedge fund behemoth he steered until stepping down to run for the Senate.

(Fox News)

The field of major candidates also includes two other wealthy contenders - Jeff Bartos, a real estate developer, philanthropist and 2018 Republican nominee for lieutenant governor, and Carla Sands, a real estate executive and major Republican donor who served as ambassador to Denmark during the Trump administration.

Without the resources available to Oz and McCormick, Barnette by comparison has spent a miniscule amount to run ads.

Barnette’s bare-bones campaign is getting some last-minute help from a group with deep pockets.

BARNETTE GETS LAST MINUTE BOOST FROM MAJOR CONSERVATIVE GROUPS

The Club for Growth, the pro-business and anti-tax group that’s a major spender in Republican primaries, recently endorsed Barnette and last week announced that it has dished out $2 million to run an ad statewide in Pennsylvania that highlights the candidate’s biography.

And Barnette also recently landed the endorsement of the Susan B. Anthony List, a leading pro-life outside group. SBA List told Fox News on Friday they were spending six-figures to run digital ads in support of Barnette.

The Democratic Senate primary, a much less crowded and combustible showdown than the GOP race, grabbed plenty of attention over the weekend when the overwhelming front-runner – Lt. Gov. John Fetterman – announced on Sunday that he hospitalized after suffering a stroke. 

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Fetterman emphasized that he’s "well on my way to a full recovery" and added that his "campaign isn’t slowing down one bit, and we are still on track to win this primary on Tuesday, and flip this Senate seat in November."

Fox News' Tyler O'Neil and Emmett Jones contributed to this report