WASHINGTON — In preventing EU Ambassador Gordon Sondland from speaking to Congress Tuesday, President Trump pulled a move he’s made countless times since taking office: Use presidential power to block an official probe into his conduct.

But Democrats, now armed with the threat of impeachment, are hoping to use that strategy against him — by adding Trump’s resistance to the case for booting him out of office.

“If they are stonewalled now, they’ll take it as further evidence of obstruction,” said Richard Arenberg, who spent more than 30 years as a Capitol Hill staffer for Democrats. “And they can drop all that evidence into a second article of impeachment.”

Trump’s White House made clear in a scathing letter to Congress Tuesday afternoon that it will make Democrats fight for every witness and document, a reversal from the earlier release of an explosive rough transcript of Trump's July 25 phone call with the president of Ukraine.

Yet the more blatantly Trump stonewalls, the more convincing any potential impeachment case against him for obstruction becomes, legal experts told VICE News. Democratic leadership is already signaling that move is coming. “The failure to produce this witness, the failure to produce these documents, we consider yet additional strong evidence of obstruction of the constitutional functions of Congress,” said Rep. Adam Schiff, chairman of the House Intelligence Committee, which announced Tuesday that Sondland would soon be served with a subpoena.

Impeaching Trump for obstruction would echo past impeachment platforms against former presidents Richard Nixon and Bill Clinton. Such a dynamic adds a new twist to the longstanding legal feud between Trump and House Democrats over testimony and documents, which has thus far been bogged down in litigation that many fear could last beyond Trump’s presidency.

The Impeachment effect

Democrats’ impeachment inquiry might just help speed up their legal fight for witnesses and documents, too, legal experts said.

Running an impeachment inquiry gives Democrats a significantly stronger legal argument in these battles because Congress’ impeachment power is explicitly enshrined in the Constitution, legal experts say.

“I think impeachment makes a tremendous difference,” said Charles Tiefer, former solicitor for the House of Representatives. “The House has now ratcheted up to a much higher level the purpose for which the documents are being sought.”

But those cases will still have to march through the court system with epic speed to succeed in time to impact their central investigation into Trump’s pressure campaign on Ukraine. And few are sure the courts will move fast enough to make that happen.

“It totally depends on what the courts want to do,” said Frank Bowman, author of "High Crimes and Misdemeanors: A History of Impeachment for the Age of Trump." “There’s no rule that says, ‘Oh, well, this is impeachment, so we have to move super fast.’ There’s just no way to know.”

Before the Ukraine scandal erupted in September, Democrats struggled to convince judges to speed their cases along. But House Speaker Nancy Pelosi’s high-profile endorsement of the impeachment inquiry in late September might help their case, even though it made no technical legal difference, said Tiefer, now a law professor at the University of Baltimore.

“All these judges will understand from a glance at the front page of their newspaper that the House is moving fast and needs the evidence even faster,” Tiefer said.

Democrats vowed Tuesday to subpoena Sondland for testimony and documents, saying the State Department was withholding his text messages relevant to Trump’s attempts to push Ukraine to investigate Trump’s 2020 rival Joe Biden.

Sondland’s attorneys said he remains willing to speak with Congress, including about his role in exchanging a series of damning text messages that appeared to show high-level diplomats trying to figure out how to get Ukraine to launch investigations.

But his plan to appear before the House was jammed by the State Department in the middle of the previous night, when a voicemail from the State Department ordered him to stand down.

Trump soon pulled the ultimate responsibility for Sondland’s failure to appear directly onto himself, tweeting: “I would love to send Ambassador Sondland, a really good man and great American, to testify, but unfortunately he would be testifying before a totally compromised kangaroo court.”

Making the decision all about himself just draws Trump even deeper into Democrats’ sights over obstruction as their impeachment inquiry presses on.

Indeed on Tuesday, House General Counsel Doug Letter told a federal judge that obstruction might be part of any impeachment platform.

"I can't emphasize enough: It's not just Ukraine," Letter said during a hearing over access to documents related to Special Counsel Robert Mueller’s Russia probe. “Another possible impeachment count is obstruction of Congress.”

Cover: Rep. Adam Schiff, D-Calif., Chairman of the House Intelligence Committee, gives a statement to members of the media on Capitol Hill in Washington, Tuesday, Oct. 8, 2019. The Trump administration barred Gordon Sondland, the U.S. European Union ambassador, from appearing Tuesday before a House panel conducting the impeachment inquiry of President Donald Trump.