Democrats on the House Judiciary Committee filed a motion Monday to expedite the panel’s lawsuit seeking to enforce a subpoena against former White House counselor Don McGahn.

In the new court filings, Democratic counsels argue their investigation, which they say is a time-sensitive matter because their probe expires in early January, is being severely delayed as a result of the White House blocking McGahn’s testimony.

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"McGahn’s refusal to testify harms the Judiciary Committee by depriving it of a witness and information that are essential to its investigation, thereby impeding the Judiciary Committee’s ability" to conduct “the most urgent duty the House can face: determining whether to approve articles of impeachment," the court document reads.

"That refusal also is impeding the Judiciary Committee in its ability to assess the need for remedial legislation and to conduct oversight of [the Justice Department]. All of these tasks are time-limited. The House, and with it the Judiciary Committee’s investigation, expires on January 3, 2021. The delay caused by McGahn’s refusal to testify thus severely impedes the Judiciary Committee’s ability to do its time-sensitive work," it continues.

House Democrats are asking a U.S. district judge in the District of Columbia to grant declaratory and injunctive relief by declaring "that McGahn’s refusal to appear before the Committee in response to the subpoena issued to him was without legal justification" and to "issue an injunction ordering McGahn to appear and testify forthwith before the Committee" about his testimony to former special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE and to other questions they may have.

Judiciary Committee Chairman Jerrold Nadler Jerrold (Jerry) Lewis NadlerDemocrats shoot down talk of expanding Supreme Court Schumer: 'Nothing is off the table' if GOP moves forward with Ginsburg replacement Top Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence MORE (D-N.Y.) and other Democrats have a lot riding on this lawsuit, with the committee describing McGahn as their “most critical witness.”

If the case is ruled favorably, they argue, a domino effect will occur in which former Trump officials who had refused to testify at the request of the White House would be compelled.

And by moving to expedite the process, Democrats hope they won’t lose too much time and interest extracting testimony from key witnesses involved in the nearly dozen episodes of obstruction by President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE, as laid out in the 448-page Mueller report.

“President Trump and the White House have repeatedly blocked witnesses from complying with Committee subpoenas and documents and continue to attempt to stall progress in the courts,” Nadler said in a statement with the recent filing. “We are aware of this strategy to prevent Congress and the American people from hearing the truth about Trump’s obstruction which is why expediting Mr. McGahn’s testimony is so very important.”

Nadler has issued a slew of new subpoenas over the House’s six-week recess in what is likely to escalate the standoff between the White House and congressional Democrats, who are conducting a sprawling investigation into possible obstruction outlined in the report and potential abuses of power by the president.

On Monday, Nadler subpoenaed former White House staff secretary Rob Porter for testimony on Sept. 17, the same day the chairman has also subpoenaed former campaign chairman Corey Lewandowski Corey R. LewandowskiTrump faces tricky choice on Supreme Court pick How Trump can win reelection: Focus on Democrats, not himself Trump Jr. distances from Bannon group, says he attended 'single' event MORE and former White House official Rick Dearborn to testify.

The Trump administration has sought to block the testimony of current and former White House aides such as McGahn, who is seen as a key witness in Mueller's report.

The White House has argued that under the standard of immunity, confidentiality protections offered to the executive branch apply to current and former aides, effectively preventing them from disclosing what took place during their time in the administration.

While both Republican and Democratic administrations have invoked the immunity concept, legal experts say there is virtually no case law on the subject, with some predicting the White House is likely to lose if it's challenged in court.

Democrats in particular consider McGahn a key witness because Trump ordered the former White House counsel to remove the special counsel — an order he refused to carry out out of fear he would trigger another Nixon era-like Saturday Night Massacre. McGahn instead drafted a resignation letter that he ultimately did not submit.

The order to remove Mueller came after the president discovered that the federal investigation was not just examining Russian interference and possible coordination between members of the Trump campaign and Russia but also possible obstruction by the president following his decision to fire former FBI Director James Comey James Brien ComeySteele Dossier sub-source was subject of FBI counterintelligence probe Judge will not dismiss McCabe's case against DOJ Democrats fear Russia interference could spoil bid to retake Senate MORE, who was overseeing the probe.

Republicans have accused Democrats of seeking to rehash the Mueller report in an attempt to damage the president heading into 2020.

And so far, the White House has maintained a strong firewall in blocking current and former staffers from testifying.

Still, the court case could shake things up for the two parties depending on how U.S. District Judge Ketanji Brown Jackson rules.

A lawyer for McGahn, William Burck, wrote in a letter earlier this month that his client would follow the White House order not to testify unless a court judge ruled otherwise.

“The President instructed Don to cooperate fully with the Special Counsel but directed him not to testify to Congress unless the White House and the Committee reached an accommodation. When faced with competing demands from co-equal branches of government, Don will follow his former client’s instruction, absent a contrary decision from the federal judiciary,” Burck said at the time of the lawsuit was filed earlier this month.

Democrats hope McGahn’s testimony would inspire a new wave of national interest as they seek to use the national spotlight on McGahn's testimony to paint a picture of a corrupt commander in chief who is unfit to lead.

The lawsuit to obtain McGahn’s testimony comes with a majority of House Democrats now in favor of formally opening up an inquiry to decide whether to introduce articles of impeachment against the president.

While Mueller did not find sufficient evidence to conclude that the Trump campaign coordinated with Russia, he did not make a determination as to whether the president obstructed justice. Attorney General William Barr Bill BarrFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Why a backdoor to encrypted data is detrimental to cybersecurity and data integrity FBI official who worked with Mueller raised doubts about Russia investigation MORE and other Department of Justice officials ultimately decided that the evidence laid out in the Mueller report did not reach the threshold needed to charge Trump.

Democrats, however, argue it was not Barr’s choice to make and that lawmakers must decide whether the president’s actions rose to the level of “high crimes and misdemeanors.”