Attorney General Jeff Sessions testifies before the Senate Intelligence Committee on Capitol Hill in June 2017. (Melina Mara/The Washington Post)

Democrats on the House Judiciary Committee are negotiating for Jeff Sessions’s testimony in their impeachment investigation of President Trump, an appearance they hope could bolster their inquiry given the former attorney general’s rocky relationship with Trump. 

Congressional aides on the panel reached out to Charles J. Cooper, an attorney for Sessions, during the summer, according to officials familiar with the discussions who spoke on the condition of anonymity to freely describe private talks. Cooper told committee staff that Sessions — whom Trump never forgave for recusing himself from overseeing the special counsel probe — would need a subpoena to testify.

“I have made clear that Attorney General Sessions will not appear except under compulsion of a congressional subpoena,” Cooper said in a phone interview this week.

The panel in mid-July approved a series of compulsory measures for Trump associates and former officials, including Sessions, who appears as a critical witness in special counsel Robert S. Mueller III’s report. The former attorney general is a key player in episodes of potential obstruction of justice investigated by the special counsel. 

A subpoena for Sessions has not yet been issued. The committee did not respond to a request for comment Friday. 

A blockbuster hearing with Sessions could infuriate Trump, who regularly ranted about Sessions, even mocking him publicly, and fired him in November after a tumultuous relationship that began in March 2017 when the attorney general recused himself from the Justice Department investigation into Russian interference.

Sessions’s No. 2, Deputy Attorney General Rod J. Rosenstein, went on to appoint Mueller in the wake of then-FBI Director James B. Comey’s firing. Mueller’s work led to the indictments of numerous Trump associates, was a cloud over Trump’s presidency for nearly two years and is a major focus of the impeachment inquiry.

Discussions about obtaining Sessions’s testimony come as the panel has escalated its investigation into whether to impeach the president. Democrats increasingly say a vote impeaching Trump this winter is inevitable — even as House Speaker Nancy Pelosi (D-Calif.) has refused to acknowledge that the panel’s work constitutes impeachment proceedings.

Democrats would likely ask Sessions about the blowback he received from Trump for his recusal, as well as his knowledge of other episodes that are described in the Mueller report. But it’s unclear how much he will be able to say if the White House tries to block his testimony. 

The former senator from Alabama was one of Trump’s earliest backers in 2016 at a time when other Republicans opposed the New York businessman, later becoming a top campaign surrogate.

Sessions’s recusal from the Russia investigation fundamentally altered his once-positive relationship with the president. Trump thought his attorney general should be loyal to him first; Sessions, however, felt he had a duty to step aside due to his close proximity to the Trump campaign and amid reports that he had met with Russians during that campaign.

One potential factor in a Capitol Hill appearance is Sessions’s political future. The 72-year-old has been mentioned as a possible candidate for his old Senate seat, which is considered a prime pickup opportunity for the GOP next year. During the summer, Sessions did not rule out a bid in a state where Trump is overwhelmingly popular.

The White House has instructed its former counsel Donald McGahn not to testify despite panel subpoenas. But that precedent likely does not apply to Sessions, legal experts say. McGahn was a White House employee working for the executive branch, while Sessions’s client was the U.S. government. 

“A subpoena requires the witness to show up,” said Stephen Gillers, a professor at NYU Law School. “He can then assert any immunity or privilege he thinks he may have. If the committee disagrees, a judge decides.”

The Justice Department declined to comment. 

According to the Mueller report, Trump repeatedly berated Sessions to his face and pressured him to reverse his recusal. Trump even tried flattery, telling Sessions he’d be a “hero” if he took charge of the investigation during a December 2017 meeting. 

In May 2017, when Sessions told Trump that Rosenstein had appointed Mueller as special counsel, the president slumped back in his chair, according to notes from Jody Hunt, Sessions’s ex-chief of staff, and declared: “Oh my God, this is terrible. This is the end of my presidency,” Trump said, adding a profanity. 

Trump further laid into Sessions for his recusal, saying Sessions had let him down.

“Everyone tells me if you get one of these independent counsels it ruins your presidency,” Trump said, according to Hunt’s notes that were cited in the Mueller report. 

According to the report, Trump also asked his former campaign manager Corey Lewandowski in June of 2017 to get Sessions to limit the special counsels’ jurisdiction to future election interference. Lewandowski, who is testifying before the Judiciary Committee on Tuesday, never followed the order — though he tried and failed to set up a meeting with Sessions.

Sessions also verified Comey’s testimony about raising concerns about Trump, the report said. Comey said Trump asked him to stop an investigation into his former national security adviser Michael Flynn — and that he later told officials, including Sessions, not to leave him alone with Trump.

Beyond the Mueller report, Trump’s anger with Sessions has been palpable over the years. In the summer of 2017, Trump regularly assailed Sessions on Twitter for failing to appoint a special counsel to investigate Hillary Clinton’s use of a private email server when she was secretary of state. 

“Attorney General Jeff Sessions has taken a VERY weak position on Hillary Clinton crimes (where are E-mails & DNC server) & Intel leakers!” he wrote.

Trump would later jab Sessions for refusing to investigate whether the FBI’s Russia investigation was tainted by bias, writing in August 2018: “This is a terrible situation and Attorney General Jeff Sessions should stop this Rigged Witch Hunt right now, before it continues to stain our country any further.”