An accelerating justice department investigation into a “fake electors” scheme to help Donald Trump overturn the 2020 election, plus explosive testimony from January 6 hearings, have created intense legal heat for the lawyers Jeffrey Clark, Rudy Giuliani and John Eastman, who were key players in the abortive effort, say ex-prosecutors.

While Giuliani and Eastman were key lawyers for Trump and his campaign, respectively, and Clark was a senior justice department official, the trio played big roles in a brazen multi-front drive not to certify some Biden electors but bogus ones for Trump. That could fuel charges against Trump, who they collaborated with, for obstruction of an official proceeding, or defrauding the US.

Recent justice department actions, including seizing electronic devices of Eastman and Clark, coupled with more evidence at committee hearings, are increasingly likely to spur charges against the three lawyers related to the drive to replace electors Biden won in seven states with fake ones for Trump, say legal experts.

The justice’s expanding criminal inquiry became palpable on 22 June when FBI agents raided Clark’s home, and separately seized Eastman’s cellphone, as grand jury subpoenas involving the scheme were served on top Republican figures and Trump allies in Georgia and Arizona.

In another stark sign of the legal jeopardy Giuliani and Eastman face, recent House committee hearings into the attack on the Capitol offered evidence that both lawyers sought pardons from Trump, presumably tied to plotting strategies to block Biden’s certification by Congress on 6 January, and fiery speeches they gave along with Trump at a rally on the Ellipse before a mob of his allies attacked the Capitol.

The legal threats facing Clark were underscored at a 23 June panel hearing by scathing testimony from former top justice officials about Trump’s plotting with Clark to elevate him to acting attorney general to push the fake electors scheme by falsely claiming in a proposed letter to Georgia officials that the department had “significant concern” about election fraud there and in other states.

The former acting deputy attorney general Richard Donoghue was scalding as he detailed Trump’s efforts to replace the acting attorney general, Jeffrey Rosen, with Clark in late December 2020, and to pressure state legislators to reject Biden electors by promoting baseless charges of widespread fraud.

Donoghue recounted how he warned Trump at a bizarre 3 January White House meeting – that was attended by Rosen, Trump counsel Pat Cipollone and other top lawyers – that elevating Clark to be acting AG would spark mass resignations, and Clark would be “left leading a graveyard”, at the department. Cipollone, who was recently subpoenaed by the House panel, also threatened to resign if Clark replaced Rosen.

Further, according to shocking testimony on 28 June by Cassidy Hutchinson, a top aide to the ex-White House chief of staff Mark Meadows, Cipollone warned her early on 6 January of potential criminal liability for Trump and others if Trump went to the Capitol as he had discussed doing, and asked Hutchinson to “please make sure we don’t go up to the Capitol”.

All of it adds up to potentially grave consequences for the three lawyers.

Michael Zeldin, an ex-DoJ prosecutor, said: “The strong evidence presented about the fake electors scheme at recent House committee hearings, including testimony by senior justice department officials, laid the foundation for charging Trump’s legal advisers, Eastman and Giuliani, and possibly Clark, with multiple state and federal crimes including obstruction of an official proceeding, conspiracy to defraud the United States, false statements in connection with the fake electors scheme, and election fraud.”

He added: “The cumulative evidence presented over the course of the hearings paint a picture of a president who was told explicitly by multiple people that he lost the election and that once he exhausted his judicial remedies (losing nearly 60 cases) his continuing pressure campaign to prevent the orderly transfer of power was illegal.

“Yet Trump and his attorneys persisted.”

Other ex-prosecutors stress that the FBI raids to obtain Clark and Eastman’s phones indicate the investigations of the two lawyers have escalated.

“Search warrants of Clark and Eastman’s phones means that a judge found probable cause to believe that evidence of a crime would be found on each of those devices,” Barbara McQuade, a former US attorney for eastern Michigan, told the Guardian.

Eastman’s exposure to criminal charges has been palpable and growing for months. In March, a federal judge, David Carter, in a crucial court ruling involving Trump’s legal adviser Eastman, stated that Trump “more likely than not” broke the law in his weeks-long drive to stop Biden from taking office.

“Dr Eastman and President Trump launched a campaign to overturn a democratic election, an action unprecedented in American history,” Carter wrote in a civil case which resulted in an order for Eastman to release more than 100 emails he had withheld from the House panel.

Other revelations damaging to Trump and Eastman emerged at a mid-June House panel hearing when Greg Jacob, the ex-counsel to former vice-president Mike Pence, provided detailed testimony about how Eastman and Trump launched a high-pressure effort to persuade Pence to unlawfully block Biden’s certification by Congress on 6 January.

The Eastman pressure included the scheme to substitute pro-Trump fake electors from states that Biden won for electors rightfully pledged to Biden. Jacob testified that Eastman acknowledged to him that he knew his push to get Pence on 6 January to reject Biden’s winning electoral college count would violate the Electoral Count Act, and that Trump, too, was informed it would be illegal for Pence to block Biden’s certification.

In mid-December 2020, at least 59 Republicans from states Trump lost falsely asserted and signed legal documents that they were “duly” chosen electors for Trump in the electoral college.

Former prosecutors say potential charges against Trump and his top lawyers have increased in part due to the powerful details that ex DoJ leaders testified about on 23 June involving how “Trump pushed to weaponize the justice department to facilitate the [fake electors] scheme,” McQuade said.

McQuade noted too that the deputy attorney general, Lisa Monaco, months ago confirmed “DoJ had received evidence from state AGs about alternate slates of electors and was investigating. It appears that DoJ is now issuing subpoenas regarding this episode … One could imagine each link leading to the next and possibly all the way to Donald Trump.”

On top of Trump’s involvement in the fake electors ploy, ex-deputy attorney general Donald Ayer, who served in the George HW Bush administration, told the Guardian that overall “the evidence is increasingly showing Trump’s culpability. Trump had extensive involvement in long conversations where he was personally working intently to overturn the election.”

Ayer’s point was bolstered by Hutchinson’s eye-popping testimony about Trump’s knowledge of, and indifference to, the large cache of dangerous weapons that were being carried by his supporters.

Paul Pelletier, a former acting chief of DoJ’s fraud section, said that for prosecutors the powerful testimony of Hutchinson “might be the final nail in the legal jeopardy coffin of Trump’s coterie of lawyers and enablers”.

“Hutchinson’s testimony has lifted the curtain on the false narrative that the violent Capitol confrontation was spontaneous,” he added.

The Democratic senator Sheldon Whitehouse sees a need for coordination of criminal investigations between the DoJ and others into the multiple efforts by Trump and key allies to block Biden’s win in Georgia, including Trump’s call to Georgia’s secretary of state, Brad Raffensperger, which is under scrutiny by the Fulton county district attorney and a special grand jury.

“Phoney electors, the Clark memo, and Trump’s phone calls all converge on Georgia,” Whitehouse told the Guardian. “I hope and expect that the investigations are coordinated. The raid on Clark shows how serious this is, and false electors could make great witnesses.”

Looking ahead, former federal prosecutor Dennis Aftergut told the Guardian prosecutors appear to be amassing growing evidence to pursue charges against the three lawyers who were central actors in various parts of the fake electors scheme.

“Giuliani and Eastman seeking pardons is powerful evidence of ‘consciousness of guilt’,” Aftergut said.

In a potential legal twist, Aftergut pointed out that if charges are filed against one of the three, prosecutors will seek their help in going after the others. “The earliest cooperators generally get the best deals from prosecutors … any of them could potentially provide damaging evidence against the other two and Trump.”