James Comey released his opening statement on Wednesday, claiming Trump expected "loyalty."
The former FBI director will speak about his interactions with Trump, including how the president demanded loyalty and made other requests.
Comey is set to testify in front of the Senate Intelligence Committee on Thursday about whether the president tried to impede the FBI's Trump-Russia investigation.
The former FBI director claims it was inappropriate for the president to ask the attorney general to leave so they could speak one-on-one.
President Donald Trump's Twitter feed will command plenty of attention during James Comey's testimony.
Leaders of progressive groups on Wednesday asked, "What is Trump hiding?"
The Senate Intelligence Committee published the former FBI director's opening statement a day before he is scheduled to testify.
President Donald Trump denied salacious memos detailing alleged interactions with Russian prostitutes in a Moscow hotel.
CNN called Thursday's hearing "Washington's Super Bowl." Are you ready?
A majority of Americans think the president is interfering with the Russia investigation, and 61 percent think he fired James Comey to protect himself.
The ads, which echo Trump's criticism of the sacked FBI director, come from one of Donald Trump's biggest donors during the election.
The presient reportedly asked Dan Coats, his director of National Intelligence, to persuade the FBI to back off its investigation into Michael Flynn.
Former FBI director James Comey will testify Thursday on the Russia probe and whether the president attempted to obstruct investigations.
Comey is to testify Thursday before the Senate Intelligence Committee, which is investigating alleged links between Donald Trump's team and Russia.
U.S. Deputy Attorney General Rod Rosenstein will be among those testifying about the firing of James Comey at a Senate hearing.
Comey's highly anticipated appearance before the Senate Intelligence Committee on Thursday could be a turning point in a controversy that has rocked Trump's young administration.
Senior Republicans reportedly said the White House has been unable to secure some of the key legal and communications staff they wanted.