Congress is increasingly turning to its most powerful weapon against President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE: oversight.

As more Democrats urge Speaker Nancy Pelosi Nancy PelosiPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' On The Money: Anxious Democrats push for vote on COVID-19 aid | Pelosi, Mnuchin ready to restart talks | Weekly jobless claims increase | Senate treads close to shutdown deadline Trump signs largely symbolic pre-existing conditions order amid lawsuit MORE (D-Calif.) to start impeachment proceedings, she has pointed to the party's recent wins in court against Trump as proof that the party doesn't need to initiate a move that comes with significant political pitfalls.

The legal history backs her up approach: Judges tend to side with Congress's oversight powers in court battles over executive privilege.

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Impeachment proponents on Capitol Hill argue that moving forward with an inquiry would strengthen Democrats’ hands when it comes to other oversight matters.

Some legal experts argue that even without impeachment, House Democrats are likely to win their court fights with the administration — even if those fights make it all the way to the Supreme Court.

“I think that Congress's role as the oversight organization is so compelling that the Supreme Court would uphold the subpoenas,” Jill Wine-Banks, a member of the special prosecutor’s team during Watergate, told The Hill.

Others, meanwhile, say that pursuing an impeachment inquiry over traditional investigations could give lawmakers an edge in court with respect to certain legal battles, especially those over materials related 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’s investigation.

“Starting an impeachment inquiry, I think, strengthens the Judiciary Committee’s hand enormously if it goes to court,” said Michael Conway, who served as counsel on the House Judiciary Committee during Watergate.

He noted that the Judiciary panel would ostensibly be the one to take up a formal impeachment inquiry.

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But others say Democrats are facing uncharted territory and that the political risks associated with impeachment might not be worth any legal advantages that come with the proceedings.

“There is the possibility a court sees more compelling reasons when it's actually in the middle of an impeachment inquiry,” Wine-Banks said. “But that's never been tested.”

The court fights could take months, significantly delaying Democrats’ investigative pursuits even if they are ultimately successful in securing the sought-after documents or testimony.

Court battles at this level also carry the inherent risk of a loss or setback that could create a damaging precedent for future Congresses or administrations.

On Tuesday, Democrats filed their first lawsuit against the Trump administration to enforce that oversight, asking a judge to compel the Treasury Department to turn over Trump’s tax returns.

Democrats are also locked in legal disputes with Trump over subpoenas they issued to private firms for his financial records, specifically Deutsche Bank, Capital One and Mazars.

Pelosi has refrained from pushing the aggressive Democratic investigations any further than court action, warning that the party isn’t prepared to start impeachment proceedings.

David Dorsen, who served as assistant chief counsel on the Senate Watergate Committee, said the House subpoenas are crafted in a way that emphasizes Congress’s power to conduct oversight, which could be enough to give lawmakers a win in court.

“Congressional oversight power is very substantial,” Dorsen said. “The major issue that has been raised is whether something is within the committees’ oversight power. And I think they've been very, very careful there. They know the problem and are careful to phrase it in terms of legislative purpose or other legitimate purpose.”

“And I think that the president would be just as inclined to ignore a subpoena of the impeachment committee as one of the other committees,” he added.

Trump has signaled he is prepared to wage a lengthy war against Democrats, who are seeking to dig up documents ranging from records on his private businesses to testimony on his private conversations in the White House relating Mueller’s probe.

The president has twice sued in his personal capacity to try to block congressional subpoenas seeking documents from private financial institutions. Democrats have scored victories in those lawsuits and are confident they will win more legal battles going forward.

While the president’s lawyers have argued that the subpoenas are politically motivated and an attempt to damage Trump ahead of the 2020 election, judges have sided with House Democrats’ claims that the document requests fall under their oversight powers and will guide them in future legislative efforts.

Jack Sharman, a former special counsel to Congress during the Whitewater investigation, noted there is a difference between subpoenas Congress issues to private firms or third parties in connection with Trump investigations and those issued to the executive branch and that courts are often reluctant to get into a fight between two coequal branches.

Sharman said opening a formal impeachment inquiry might aid lawmakers in court as they argue that they are within their power to make requests for documents and testimony, but it would not guarantee legal victory in tussles over subpoenas to the executive branch.

“That would provide certainly some atmosphere that I think the committees could use in the litigation to say that this is clearly within our power — that is, an impeachment investigation — and these subpoenas are in aid of that express power, so the courts need to aid us essentially in this charging power constitutional duties,” Sharman said.

“That’s fine as far as it goes, but how far does that get you?” he added.

White House lawyers have argued that the congressional subpoenas serve no legitimate legislative purpose. But experts roundly criticize that argument as weak, noting the broad scope of Congress’s authority to investigate.

“I don’t think that is the administration’s strongest argument because the scope of permissible congressional investigation is very broad. Basically, it is as broad as anything that is germane to legislation,” Sharman said. “And of course, legislation — there is almost nothing Congress cannot legislate on.”

The administration has also invoked the concept of immunity for senior presidential advisers from compelled congressional testimony as a way to avoid individuals such as ex-White House counsel Don McGahn from discussing their work in the West Wing with congressional investigators.

Trump, meanwhile, has invoked executive privilege over documents subpoenaed by Congress, as the White House has repeatedly declined to provide records that could implicate matters of executive privilege without a formal invocation.

Historically, fights between the legislative and executive branches over subpoenaed materials have been worked out between the two parties without the judicial branch getting involved.

For example, Congress subpoenaed former White House counsel Harriet Miers, who worked under then-President George W. Bush, to compel her to testify about the firing of U.S. attorneys by the administration. While she initially resisted the subpoena, citing immunity, a district court ruled that Miers still had to show up to testify.

She appealed that ruling, but it was settled out of court before the appellate judges could decide the case.

One key area where impeachment efforts could help Democrats is their quest to obtain some redacted portions of the 448-page Mueller report.

The grand jury information in the report has remained under seal, pursuant to federal rules, but courts have found that those details can be released under certain circumstances, particularly as part of an impeachment proceeding.

House 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.) has pressed Attorney General William Barr Bill BarrHillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Bipartisan representatives demand answers on expired surveillance programs YouTube to battle mail-in voting misinformation with info panel on videos MORE to join him in petitioning a court for the material’s release, but the attorney general has declined. Nadler had threatened to hold Barr in criminal contempt over his failure to turn over Mueller’s full report and evidence, though he backed off in June after the Justice Department began sharing some of the underlying files.

Wine-Banks said the grand jury information could even be released now, as Congress conducts investigations related to the Mueller report while it debates impeachment.

She said that when the special prosecutor in Watergate sought President Nixon’s secret Oval Office tapes, it was before the prosecutor had begun any formal proceedings.

“It was pretrial. It's preliminary to [a proceeding]. And the court said, yes, that was legitimate,” Wine-Banks said. “And I think the same would be true here.”