The Pennsylvania GOP Senate candidate has ties to the Turkish government and military, according to former Secretary of State Mike Pompeo.
Oz voting in the Turkish election and serving in the Turkish military are some of the questions that Pompeo has about Oz.
The questions need to be answered as they will be asked while determining Oz's eligibility for a clearance as a member of Congress.
The former secretary of state called for Oz's campaign to provide an explanation for why Oz was able to vote in a Turkish election but not in an American election.
Oz's campaign did not respond to a request for comment from Forbes, but told ABC News there was no security issue with Oz voting in the Turkish election.
Oz has never been involved with the political work of the Turkish government, his spokeswoman Brittany Yanick told ABC News.
Trump endorsed Oz last month, setting up a clash between the backing power of the two men. Trump and Pompeo have not yet announced runs for the White House, though the Secretary of State said in an interview with Fox News that any potential decision will be independent of what Trump decides.
In Ohio's Republican Senate primary on Tuesday, Trump appeared to be a major factor. J.D. Vance, a lawyer and former Trump critic, became the winner of the primary after Trump endorsed him. Trump's endorsements have not always been the deciding factor in races.
About 20,000 people are expected to attend the Oz rally hosted by Trump in Pennsylvania on Friday, where he will be speaking with his friend and adviser, Vance. Pennsylvania's primary will be held on May 17.
The TV show will end after Dr. Oz gets a GOP Senate seat.
The vote of Dr. Oz in the Turkish election renewed criticism.
The latest test of Dubious Endorsement Power is reported by Forbes.
The Ohio Senate primary was won by a Trump-backed candidate.