Republican Senate candidate Mehmet Oz speaks at a campaign event in Bristol, Pennsylvania, on April 21, 2022, with former US Housing and Urban Development Secretary Ben Carson, left.
CNN  — 

Republican Senate candidate Dave McCormick has honed in on a closing message in the final days before the May 17 Pennsylvania primary: questioning the patriotic loyalties of his main primary opponent, Mehmet Oz.

In a Friday press briefing organized by McCormick’s campaign, former US Secretary of State Mike Pompeo spoke about Oz’s “connection to the Turkish government.” Citing the revelation of a photo this week that showed the American-born Oz, a dual citizen of the United States and his parents’ native Turkey, casting a ballot in the 2018 Turkish presidential election, Pompeo called on Oz’s campaign to “explain why he had time and energy and focus to vote in a Turkish election, but not in an American election.”

“Maybe it’s all innocent, maybe it’s all straight up, but we and the people of Pennsylvania and the Americans who he will be representing as one of a hundred members of the United States Senate voting on important national security matters need to understand the scope and depth of his relationship with the Turkish government,” Pompeo said.

Oz campaign spokeswoman Brittany Yanick called the criticisms from McCormick’s campaign “pathetic and xenophobic.” She asserted that his Turkish citizenship posed no security threat to the United States and noted that Oz “has already said when elected to the Senate he would renounce his citizenship.” She did not respond to questions about whether Oz voted in any US elections in 2018.

The 2018 photo, posted on the Facebook page of the Turkish Consulate General in New York, shows Oz placing a paper ballot into a ballot box. The post noted that Turkish citizens registered on foreign electoral rolls were eligible to vote at the consulate. ABC News first reported the existence of the picture.

In February, Oz told Washington Post columnist Josh Rogin that he had “never been politically involved in Turkey in any capacity.”

Yanick confirmed the photo’s authenticity, telling CNN that “voting in an election is far different from being actively engaged in the political work of the Turkish government, which Dr. Oz has never been involved with.”

Going after a candidate’s loyalty to the US may be a page out of the hard-line political playbook – the kind used by former President Donald Trump, who as a candidate in 2016 accused an American-born judge of Mexican descent of being biased against him in a then-class action case against Trump University because of the Republican’s pledge to build a wall on the US-Mexico border.

But despite McCormick taking up this line of attack, Trump has found himself on the other side in the primary. He endorsed Oz last month after direct lobbying by both candidates for Trump’s support.

“Now that (McCormick) 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,” Yanick said in a statement to CNN.

The Pompeo press conference on Friday follows months of efforts by the McCormick campaign to attack Oz for his ties to Turkey. After the Oz campaign accused McCormick, a former hedge fund executive, of being cozy with China in a TV ad this winter, McCormick campaign spokeswoman Jess Szymanski shot back, “How can he claim to be America First when he has dual loyalties?”

And in one McCormick TV ad released last month, a man speaking directly to the camera said that Oz “was in the Turkish army for cryin’ out loud.”

Oz’s campaign has said he kept his Turkish citizenship in order to care for his ill mother, who lives there. And in a 2011 interview, long before launching his Senate campaign, Oz said that before becoming a television personality, he served in the Turkish military in order to maintain that citizenship. The Oz campaign said his service amounted to 60 days.

“Mehmet Oz chose to serve in the Turkish army over the US army,” Szymanski told CNN. “These are simple facts, not campaign attacks, and his refusal to address these legitimate issues demonstrates why Pennsylvanians can’t trust him.”

During’s Friday’s news conference, Pompeo acknowledged that Oz’s Turkish citizenship does not legally bar him from serving in the US Senate but said the information was still relevant for voters making up their minds.

“This isn’t about whether it’s lawful, it’s about whether he is best suited to be the next United States Senator from Pennsylvania that’s been represented by a patriotic American conservative for an awfully long time,” Pompeo said. McCormick and Oz are among several Republicans competing for the party nomination to succeed retiring GOP Sen. Pat Toomey.

The major GOP candidates – who include former US ambassador to Denmark Carla Sands, businessman Jeff Bartos and conservative commentator Kathy Barnette – have faced off in two debates in recent weeks.

Pompeo’s support for McCormick – a fellow West Point cadet who graduated one year behind the Kansas Republican – represents a notable break with the former President. Pompeo, who has emerged as a potential 2024 candidate, served Trump first as his CIA director and later as secretary of state.

Trump headlined a rally for Oz in Western Pennsylvania on Friday night that also featured other Republicans the former President has endorsed, including Ohio Senate candidate J.D. Vance, who won his primary earlier this week, and US Rep. Alex Mooney, who faces a competitive GOP House primary in West Virginia on Tuesday.

CNN’s Alex Rogers contributed to this report.