WASHINGTON — As investigations by the Trump administration and its congressoinal allies into the president’s political foes intensify, House Oversight Committee Chair James Comer, R-Ky., announced Thursday he is demanding testimony from key staffers to former President Joe Biden and his physician, Dr. Kevin O’Connor.

The renewed focus on Biden’s health comes on the heels of the former president's announcement that he has prostate cancer and a new book detailing concerns from Biden administration officials about his capacity to do the job of president as he sought reelection last year. Both President Donald Trump and Vice President JD Vance raised questions about a potential cover-up of Biden’s declining mental ability and specifically speculated on his medical team’s role in obscuring the then-president’s mental and physical health from the public.

Trump has repeatedly questioned Biden’s mental acuity this week and the role his staffers may have played, including while speaking to reporters alongside House Speaker Mike Johnson at the Capitol on Tuesday. In a social media post also on Tuesday, Trump claimed Biden, 82, was “cognitively impaired” and that his staffers “stole the Presidency.”

“Something very severe should happen to these Treasonous Thugs that wanted to destroy our Country,” Trump wrote. 

Comer had issued subpoenas for some Biden staffers last year, but the Biden administration blocked the testimony. Now, he’s restarting the process with letters demanding that targets of his probe sit for transcribed interviews with committee investigators by June 25. Subpoenas could follow if the staffers decline to testify voluntarily, Comer told Newsmax on Wednesday.

“The cover-up of President Biden’s obvious mental decline is a historic scandal," Comer said in a Thursday statement, mentioning the baseless speculation that Biden’s staff used an autopen to sign official actions and pardons without his knowledge. "The American people deserve to know when this decline began, how far it progressed, and who was making critical decisions on his behalf. The American people demand transparency and accountability now.”

Comer is demanding testimony from O'Connor, former top domestic policy adviser Neera Tanden, former deputy chief of staff Annie Tomasini, former Deputy Director of Oval Office Operations Ashley Williams and Anthony Bernal, a former assistant to both Biden and first lady Jill Biden. A request for comment from Biden’s post-presidential team — where Tomasini, Williams and Bernal remain employed in varying capacities — did not immediately receive a response Thursday. 

Tanden did not respond to a request for comment sent to the Center for American Progress, the liberal think tank she helped found and then ran before and after her time in the Biden White House.

O’Connor, who first worked as Biden’s physician during the Obama administration and continued to treat and consult the Biden family during their years out of Washington, could not immediately be reached for comment. It is not clear how laws protecting doctor-patient confidentiality could interfere with any testimony he could give, if he were even willing to appear before the committee. 

“The Committee remains interested in whether your financial relationship with the Biden family affected your assessment of former President Biden’s physical and mental fitness to fulfill his duties as President,” Comer wrote in his letter to O’Connor. “Given your connections with the Biden family, the Committee seeks to understand if you contributed to an effort to hide former President Biden’s fitness to serve from the American people.”

The investigation follows Comer sparking a Justice Department probe into former New York Gov. Andrew Cuomo, a Democratic candidate for New York City mayor, this week. And it comes as, just four months into his second term, Trump has wielded the federal government against his political, personal and ideological enemies, from former government officials and Democratic lawmakers to universities and media outlets to pro-Palestinian activists and immigrants.

Earlier this week, Trump called for investigations into Vice President Kamala Harris and her campaign, a slew of celebrities, the Biden administration and former President Barack Obama. On Monday, his former personal attorney Alina Habba — now the acting U.S. attorney in New Jersey — announced criminal charges against a Democratic member of Congress over an incident at a Newark Immigration and Customs Enforcement facility. And former FBI Director James Comey, a longtime source of Trump’s ire, was interviewed by the Secret Service after sharing an image of rocks on a beach that Trump and his allies interpreted as a death threat.

Massachusetts Rep. Steven Lynch, a Democrat temporarily serving as his party’s top member on the House Oversight Commitee, did not immediately return a request for comment on Comer’s latest probe. The committee’s top Democrat, Rep. Gerry Connolly, took a step back from his work in April and died earlier this week at 75 after a battle with esophageal cancer.