Television icon Oprah Winfrey declined to explicitly endorse one of her media proteges, Dr. Mehmet Oz, in his campaign for a U.S. Senate seat in Pennsylvania.

Winfrey's comments were published on Tuesday by New York Magazine reporter Olivia Nuzzi, who was provided with a short statement by Winfrey's representative. Nuzzi had also asked for a sit-down chat with the entertainment mogul, but she was told that Winfrey was not conducting interviews.

"One of the great things about our democracy is that every citizen can decide to run for public office," Winfrey's statement read. "Mehmet Oz has made that decision. And now it's up to the residents of Pennsylvania to decide who will represent them."

Oz, 61, initially announced in November that he was running as a GOP candidate to replace the vacancy created by retiring Senator Pat Toomey, stating that his training "positioned me to make difficult decisions to help people in need and fight to empower my viewers." Now, as he continues to ramp up his campaign in Pennsylvania, the refusal to endorse Oz comes from the person who made him a household name in the eyes of many.

A graduate of Harvard University, the cardiothoracic surgeon became a regular guest on Winfrey's eponymous daytime series, The Oprah Winfrey Show, starting in the 2000s, and the host would often refer to Oz as "America's doctor."

Oz would appear on the show to answer questions and offer medical advice, and was soon one of the most visible television doctors. His success soon led to Winfrey producing multiple shows that bore his name, including Discovery Health Channel's Second Opinion With Doctor Oz and The Doctor Oz Show on Oprah's own network, Harpo Productions.

The latter will cease production in January due to Oz's ongoing Senate campaign.

Dr Oz
Oprah Winfrey has declined to explicitly endorse her one-time protege, Dr. Mehmet Oz, for his campaign for a Senate seat in Pennsylvania. Oz was a longtime guest on Winfrey's daily talk show, the Oprah Winfrey Show, in which he would dispense medical advice. Here, Oz can be seen giving a speech this past September during an annual health summit in New York City. Leigh Vogel/Getty

However, despite his significant visibility, Oz has also been mired in controversies throughout his career in medicine and television. In particular, critics have pointed towards his use of pseudoscience and unproven treatments for a variety of illnesses, and HuffPost has referred to Oz as a "quack" doctor.

"[Oz] has peddled some bizarre and potentially dangerous cures for everyday ailments, including COVID-19," HuffPost reported earlier in December. "Oz has promoted everything from raspberry ketones, berry-red pills promising to melt excess fat, to hydroxychloroquine, an antimalarial drug falsely touted by former President Donald Trump and the right-wing as a COVID-19 miracle cure."

Additionally, a group of prominent doctors wrote a letter in 2015 asking Columbia University to remove Oz from its medical board, stating that he was "guilty of either outrageous conflicts of interest or flawed judgements about what constitutes appropriate medical treatments, or both."

Oz's association with the GOP and right-wing viewpoints may have contributed towards Winfrey's hesitancy to endorse her one-time ally. While she has hesitated to talk in significant terms about her political views, once describing herself as "apolitical," Winfrey has aligned herself with prominent liberals in the past.

This includes past endorsements of former President Barack Obama and former Secretary of State Hillary Clinton during their respective presidential campaigns in 2008 and 2016.

Some members of the Democratic Party have reportedly encouraged Winfrey to run for president, especially after a speech she gave at the 2018 Golden Globe Awards in which she said that "a new day is on the horizon!"

Winfrey also reportedly made calls to undecided voters in Texas during the 2020 election encouraging them to head to the polls.

Newsweek has reached out to Oz's campaign for comment.