The U.S. House of Representatives committee that would handle any impeachment of President Donald Trump convened a hearing today with another empty chair at the witness table, as former White House counsel Don McGahn refused to testify.

In a further escalation of a struggle between Trump and Congress over its power to investigate him, the White House on Monday told McGahn, who left his post in October, to disregard a subpoena from the Democratic-led House judiciary committee subpoena to appear at the hearing.

Committee chair Jerry Nadler said Tuesday the Democrats were prepared to go to court to compel McGahn to appear, stating, “our subpoenas are not optional.”

The panel is investigating Trump and special counsel Robert Mueller’s inquiry into Russian election meddling. Attorney General William Barr on May 2 also snubbed the committee, which later voted to hold him in contempt of Congress for not handing over an unredacted copy of Mueller’s final report.

At the hearing that Barr skipped, an empty witness chair figured prominently and a Democratic committee member put a ceramic chicken on the table in front of it for the cameras. There was no sign of a repeat chicken appearance on Tuesday.

Trump is stonewalling numerous congressional inquiries into himself, his turbulent presidency, and his family and sprawling business interests, which he did not divest or put into a blind trust when he took office in January 2018.

Lone Republican dissenter

Trump and most fellow Republicans in Congress dismiss the inquiries as political harassment ahead of the 2020 elections.

However, House Republican Justin Amash, a frequent Trump critic and outspoken Michigan conservative, said over the weekend that the president “has engaged in impeachable conduct.”

Trump told reporters on Monday outside the White House that Amash is “a loser.”

Any impeachment effort would begin in the House, led by the judiciary committee, before action in the Republican-led Senate on whether to remove Trump from office.

Late on Monday, the Department of Justice issued a legal opinion saying McGahn did not need to appear at the hearing, while McGahn’s lawyer, William Burck, wrote that his client would not testify before the committee unless it reached an agreement with the White House.

Republican Congressman Justin Amash said he believed Trump committed impeachable acts after reading the Mueller report, leading to a social media attack from the president. (Carly Geraci/Kalamazoo Gazette via AP)

In a letter sent to McGahn, Nadler told the former White House counsel that he would “risk serious consequences” if he failed to show up to testify.

“Should you fail to do so, the committee is prepared to use all enforcement mechanisms at its disposal,” Nadler wrote.

On another front, in a legal setback for Trump, a U.S. judge on Monday ruled against him in a case involving another House panel. The House’s oversight committee has subpoenaed Trump’s financial records from his longtime accounting firm Mazars LLP.

In an unusual move, lawyers for Trump and the Trump Organization, his company, last month sued to try to block the subpoena. U.S. District Judge Amit Mehta in Washington ruled against Trump and denied his request for a stay pending appeal.

Early on Tuesday, Trump appealed the judge’s ruling, challenging “all aspects” of Mehta’s decision.

As the confrontation between Trump and Congress has intensified, Democrats have raised growing concerns about the president’s conduct, especially since the mid-April release of the Mueller report.

“We simply cannot sit by and allow this president to destroy the rule of law … If Mr. McGahn doesn’t testify tomorrow, I think it is probably appropriate for us to move forward with an impeachment inquiry,” Democratic Representative David Cicilline, a Judiciary Committee member, told MSNBC on Monday.

The redacted, 448-page report from special counsel Mueller, 22 months in the making, showed how Moscow interfered in the 2016 U.S. presidential election in Trump’s favour and detailed Trump’s attempts to impede Mueller’s probe.

The report found there was insufficient evidence to allege a criminal conspiracy between Moscow and the Trump campaign. It made no recommendation on whether Trump obstructed justice, leaving that question up to Congress.