After taking a hit from a leading rival as he jumped into a competitive and combustible Republican Senate primary in the key battleground state of Pennsylvania, former hedge fund executive David McCormick returned fire.

As McCormick, a West Point graduate, Gulf War combat veteran and former Treasury Department official in former President George W. Bush's administration, officially launched his bid to try and succeed retiring GOP Sen. Pat Toomey in a race that could decide whether the Republicans win back the Senate majority in the midterms, top rival Dr. Mehmet Oz quickly criticized McCormick over his former hedge fund’s considerable investments in China.

McCormick, in an interview with Fox News Digital a couple of hours later, accused Oz and his campaign of "telling lies about me," urged his rival to "renounce" his dual citizenship with Turkey, and questioned why some of Oz’s merchandise was made in "Chinese factories."

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Even before McCormick’s campaign launch, a pro-Oz super PAC blasted him over Bridgewater Associates' major investments in China. McCormick joined the hedge fund behemoth a dozen years ago and helped steer Bridgewater Associates from 2017 through the end of last year. The fund has made major investments in China.

Ahead of McCormick’s announcement, a super PAC supporting Oz went up with digital ads charging, "David McCormick, he’s a friend — of China, with a long record of selling us out." The group, American Leadership Action, planned to start targeting McCormick with TV spots on Thursday.

And minutes after news broke of McCormick's entry into the race, Oz campaign manager Casey Contres charged that "Beijing’s favorite candidate David McCormick’s deep ties to the Chinese Communist Party aren’t just problematic, they are dangerous."

Oz, the well-known celebrity physician, cardiac surgeon, and author who until his campaign launch last month hosted TV’s popular "Dr. Oz Show," didn’t take direct aim at McCormick, but in an interview Thursday on Fox News’ "The Brian Kilmeade Show," argued that "our leaders have not been strong enough in declaring the extensional threat that China is to us."

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McCormick, in an opinion piece on FoxBusiness.com as he launched his campaign, vowed that if elected "I will do everything in my power to end our dependence on China, protect our communities and our jobs, counter their attempts to reshape the world in their authoritarian image, and ensure America remains the world’s unrivaled military and economic superpower."

And in an interview with Fox News Digital, McCormick touted that "my track record and my experience puts me in a great place to be a real strong force on China and essentially putting us in a much stronger position and really taking a much stronger posture on them."

And spotlighting his support for former President Donald Trump’s America First agenda, McCormick said "The truth is I’ve always been America First, since attending West Point and putting on the uniform to represent our country in combat. And for that reason I’m the best candidate to take on China, because I’ve fought before on the battlefield and in the boardroom."

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Many GOP candidates hoping for an endorsement by Trump – who remains very popular with Republican voters as he continues to play a kingmaker’s role in party politics and flirts with a 2024 White House run. And they've spotlighted their support for the former president’s America First policies, which included a confrontational stance against China.

McCormick then returned fire against Oz.

"I’ve been in the race for 12 hours, and they’re already telling lies about me and Mehmet Oz is telling lies about me. He’s pretending to be an outsider, but I can’t think of a more DC insider play than lying to benefit yourself," McCormick charged.

Responding, Oz campaign manager Contres told Fox News that McCormick "was raising funds for a third Chinese investment fund as recently as TWO months ago while he was already exploring a Senate run. His claims to being tough on China are a lie.

And the Oz campaign pointed towards a November Wall Street Journal report that McCormick's previous firm raised the equivalent of $1.25 billion for its third Chinese investment fund, boosting the hedge fund firm "into the ranks of the biggest foreign managers of private funds" in China.

McCormick, in his Fox News Digital interview, nodding to Oz’s dual citizenship that he holds with Turkey, also called "on Mehmet Oz to renounce his citizenship."

Oz, who as a dual citizen is legally permitted to serve in Congress, has indicated he has no intention of renouncing his Turkish citizenship. And Oz’s campaign has pointed to an opinion piece the candidate wrote in which he said he’s kept his Turkish citizenship to make it easier to visit family, including his mother, who lives in Istanbul and suffers from Alzheimer’s. In his op-ed, Oz also noted that he has "deep concerns about many of its (Turkey’s) authoritarian polices and harmful foreign policies."

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Oz has also highlighted China as he runs for the GOP Senate nomination and one of the top issues on his campaign website is getting "tough on China."

"Dr. Oz believes the United States has failed to respond to the global Chinese threat," the text reads. "Every year we see more and more companies ship American jobs overseas, while failing to stand up to China as they steal our intellectual property and manipulate their currency. Dr. Oz believes we need to focus on creating jobs here in America."

David McCormick Pennsylvania Senate

David McCormick, the former CEO of a giant hedge fund, declared his candidacy for Senate on Thursday, Jan. 13, 2022, formally joining a crowded field of Republican contenders vying for the GOP nomination in the key battleground state of Pennsylvania. (McCormick Senate campaign)

But McCormick took aim at his rival for some "Dr. Oz Good Life" products that were made in China. He noted that the items were made "in Chinese factories" and asked "Why doesn’t he manufacture his products right here in Pennsylvania?"

McCormick and Oz, who have the ability to self-fund their campaigns, both have ties to Trump, and each candidate is being helped by veterans of Trump's presidential campaigns and White House, and both have met with the former president.

But McCormick has an extra tie - his wife, Dina Powell McCormick, served as deputy national security adviser in the Trump administration. 

McCormick and Oz two of the top candidates in a crowded field of Republican contenders. Among the other leading GOP candidates are a real estate developer, philanthropist, and the 2018 Republican nominee for lieutenant governor, Jeff Bartos; Carla Sands, a real estate executive and major Republican donor who served as ambassador to Denmark under Trump; and veteran and conservative political commentator Kathy Barnette.

The Democratic Senatorial Campaign Committee, the reelection arm of Senate Democrats, argued that "McCormick’s announcement makes the chaotic, vicious and expensive GOP Senate primary in Pennsylvania even worse. McCormick’s Republican rivals are already calling him out as an outsourcer who sent Pennsylvania jobs to China, a Wall Street CEO who profited at the expense of working families and yet another carpetbagger with no real connection to the Commonwealth."

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And DSCC spokesperson Jazmin Vargas predicted that "with attacks like these already flying, the GOP’s primary is sure to drain Republicans’ resources and demonstrate the deep flaws in every one of their candidates."

Expect the campaign crossfire to continue – and intensify – ahead of the May 17 primary. And the rhetoric may also get heated in the battle for the Democratic Senate nomination. Seven Democrats are running for their party's nomination, including Lt. Gov. John Fetterman and Rep. Conor Lamb.