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Former President Donald Trump teams up Friday evening in Pennsylvania with Mehmet Oz, the GOP Senate candidate he recently endorsed in the key battleground state’s crowded, combative and extremely expensive Republican Senate contest with a week and a half to go until primary day in the Keystone State.

Trump’s visit comes with the latest public opinion poll indicating Oz holding a razor-thin edge over two of his top primary rivals in the GOP battle to succeed retiring Republican Sen. Pat Toomey in a race that could ultimately decide if Republicans win back the Senate majority in November’s midterm elections.

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But hours before the rally at the Westmoreland County Fairgrounds in the small city of Greensburg, southeast of Pittsburgh, the issue of Oz’s ties to Turkey were firmly back in the political spotlight. 

Mehmet Oz speaks during the Conservative Political Action Conference in Orlando, Florida, on Feb. 27, 2022. 

Mehmet Oz speaks during the Conservative Political Action Conference in Orlando, Florida, on Feb. 27, 2022.  (Tristan Wheelock/Bloomberg via Getty Images)

The rally comes after Secretary of State Mike Pompeo – a Trump ally who served as CIA director and America’s top diplomat during the former president’s administration, but who’s endorsed and campaigned for fellow West Point graduate David McCormick, Oz’s top rival for the nomination – raised national security clearance questions over Oz’s multiple Turkish connections.

Pompeo, a Fox News contributor, repeatedly emphasized on a call with reporters that there are “things that we don’t know about his connection to the Turkish government,” and that Oz “owes the people of Pennsylvania an explanation,” because voters “need to understand the scope and depth of his relationship with the Turkish government.”

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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,” has faced questions over his dual citizenship with Turkey since declaring his candidacy. He’s repeatedly explained that he’s maintained his dual citizenship in order to take care of his mother, who lives in Istanbul and suffers from Alzheimer’s.

He’s also noted numerous times during his Senate campaign that his service in the Turkish military – for 60 days during the 1980s – was done in order to maintain his dual citizenship.

Oz, who also has an endorsement deal with Turkey’s half-government owned national airline, came under attack by McCormick at a debate on Wednesday, which is likely the last showdown between the two top contenders for the GOP nomination ahead of the May 17 primary.

McCormick, a former hedge fund executive, Gulf War combat veteran and Treasury Department official in former President George W. Bush‘s administration, asserted that Oz was “compromised” for serving in the Turkish military.

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The latest flashpoint is a photograph of Oz voting in Turkey’s 2018 presidential election. The photo, first reported by ABC News, comes from Turkey’s New York City consulate’s Facebook page, where the Oz campaign confirms their candidate voted. But Oz’s team denied that his casting of a ballot amounted to “political involvement” with Turkey.

Pompeo noted that American politicians are often criticized for failing to vote, but that Oz “chose to vote in a Turkish presidential election, but not in an American election… That raises in my mind lots of judgments about his priorities. And we need to get him and his team to explain why he had time and energy and focus to vote in a Turkish election, but not in an American election.”

In response, Oz spokesperson Brittany Yannick stated that “these are pathetic and xenophobic attacks on Dr. Oz by David McCormick, who should be ashamed of himself. Now that he lost President Trump’s endorsement, he’s resorted to sad and desperate attacks that are no different than the tropes used against Catholics and Jews.”

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Pointing to comments Oz first made to Fox News in March, Yannick noted that “Dr. Oz has already said when elected to the Senate he would renounce his citizenship. There is no security issue whatsoever, and David McCormick knows that Dr. Oz has maintained his dual citizenship to make it easier to help care for his mother who has Alzheimer’s and lives there.”

But Pompeo told Fox News on Friday, “I don’t view this as political. This is separate and apart from politics. This is about making sure that the voters have the opportunity to know all of the things, the good characteristics and the shortcomings, of candidates who are running. And the questions, in my judgment, have not been answered satisfactorily… I want to make sure that I do everything I can to get the information in the hands of the voters that they can use to make a truly informed judgment about the people that they’re voting for. That’s the reason for me jumping on this call this morning.”

Pompeo also noted that “elected officials get clearances as a result of them having been elected.”

“It’s why this matter needs to be clarified, brought to a conclusion so that Pennsylvania voters can know what it is that they’re doing and so that the American people can have confidence that every one of their leaders…. [is] fit for duty as a member of the House of Representatives, in this case, the United States Senate from Pennsylvania,” he emphasized.

The Oz campaign provided a quote from national security expert William Jr. Parker III, who noted that Oz “is a first generation American who was born on U.S. soil.”

Parker, a retired senior U.S. Navy officer and former president and CEO of the East West Institute, stressed, “I have watched him [Oz] protect the health and welfare of countless Americans and others in need. Dr. Oz is an America-First candidate and we would be fortunate to have him representing us in the U.S. Senate.”

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More than 15 months removed from the White House, Trump remains the most popular and influential politician in the GOP, as he continues to endorse Republican candidates up and down the ballot and hold rallies across the country for some of the top contenders he’s backed.

Trump took plenty of credit earlier this week when another candidate he recently backed in another jam-packed and divisive GOP Senate primary – former hedge fund executive and best-selling author J.D. Vance – won the Senate nomination in neighboring Ohio.

Senate candidate J.D. Vance greets former President Donald Trump at a rally at the Delaware County Fairground, April 23, 2022, in Delaware, Ohio.

Senate candidate J.D. Vance greets former President Donald Trump at a rally at the Delaware County Fairground, April 23, 2022, in Delaware, Ohio. (AP Photo/Joe Maiorana, File)

Vance will also speak at Friday night’s rally in Pennsylvania.

Trump has also invited Rep. Alex Mooney of West Virginia, from another neighboring state, to speak at the rally.

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Mooney, who’s being backed by Trump, is facing off on Tuesday in a GOP congressional primary with Republican Rep. David McKinley.

The state lost a congressional seat during the once-in-a-decade congressional reapportionment and both Republican incumbents were drawn into the same district. The showdown, as with the Ohio and Pennsylvania GOP Senate primaries, has partially turned into a test of the former president’s clout.

Fox News’ Courtney De George contributed to this story