Hunter Biden attributes his father's poor debate performance to Ambien use and exhaustion as House Republicans expand investigation into the former president's cognitive abilities.

In a YouTube interview on Monday, Hunter Biden said his father, former President Joe Biden, was taking Ambien during his disastrous presidential debate in 2024.

FOX News correspondent Aishah Hasnie reports on former Biden chief of staff Ron Klain's testimony in a closed-door House subcommittee hearing on President Joe Biden's cognitive decline. BRET BAIER, FOX NEWS HOST: We are learning tonight some of what the man who was chief of staff to President Biden has to say about his -- the president's mental health while in office.

Joe Biden's alleged Ambien use raises questions, as the medication is contraindicated for those requiring mental alertness, according to industry guidelines.

They give him Ambien to be able to sleep,” the former president’s son claimed. “He gets up on stage, and he looks like he’s a deer in the headlights. And it feeds into a f–king story that anybody wants to tell.

Aggravated and unleashed, former first son Hunter Biden is on something of a grudge tour, lashing out at those who pressured his father to sub out of the presidential race in the fourth quarter of the 2024 presidential election.

In wide-ranging remarks, the former president's controversial son lashed out at George Clooney, a number of Democratic strategists, and President Trump.

Anita Dunn, a longtime Biden senior adviser, has made “$40 to $50 million” off of work for the Democratic Party, Hunter Biden said. James Carville, adviser to former President Bill Clinton, “hasn’t run a race in 40 f——— years.”