Dr Oz, 61, host of the popular show called The Dr Oz Show, announced earlier this month that he would be running for the US senate.
A conservative Republican, the celebrity cardio surgeon became a household name as a guest on Ms Winfrey’s show before starting his own in 2009.
In a statement to The New York Magazine, Ms Winfrey said: “One of the great things about our democracy is that every citizen can decide to run for public office.”
“Mehmet Oz has made that decision. And now it’s up to the residents of Pennsylvania to decide who will represent them,” she added.
While Ms Winfrey has not explicitly endorsed Dr Oz, a producer on The Dr Oz Show told the Daily Beast that there was “no way that Oprah is going to help turn Pennsylvania red. Oprah is not gonna do that.”
Ms Winfrey would frequently call Dr Oz on her show throughout the 2000s and referred to him as “America’s doctor”.
He would answer questions and give medical advice on the show, after which he soon became one of the more visible doctors on television. He then moved on to his own show, which became popular as well.
Earlier this month, Sony announced that it would end the show because of Dr Oz’s run for senate.
Currently in season thirteen, the show will air its last episode on 14 January.
The Pennsylvania senate race could be widely reshaped by his entry which is now lacking a recognisable Republican face.
He is likely to be a top contender for nomination, though concerns of him being a political newcomer remain.
Dr Oz has also been a controversial figure for his medical advice which has faced criticism from experts for not being based in factual science.
He had also served as an unofficial adviser to former president Donald Trump on the Covid pandemic, though he has not been an openly outspoken loyalist.
On the other hand, there was speculation around the 2020 elections that Ms Winfrey would run for president against Mr Trump, after her speech at the Golden Globe awards in 2018. But she has insisted in interviews that she would never run for office.
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