House Speaker Nancy Pelosi’s declaration Tuesday of an “official impeachment inquiry” was a moment of singular drama in the long-running clash between President Trump and congressional Democrats, but it left unsettled key questions about how that investigation will unfold.

Among them: How sweeping will the probe be? How long will it last? Who will conduct it? And will Pelosi’s unilateral pronouncement — which was delivered with no immediate plans to ratify it with a House vote — do anything to change the course of existing investigations that have hit a stone wall of White House resistance?

Pelosi (D-Calif.) on Tuesday gave only a cursory outline in her public remarks, noting that she would be “directing our six committees to proceed with their investigations under that umbrella of impeachment inquiry.” In a closed-door meeting of Democratic lawmakers Tuesday, she was only slightly more voluble — promising an “expeditious” inquiry, according to lawmakers present.

The lack of detail about the road ahead, according to interviews with more than a dozen Democratic lawmakers and aides, reflected both the speed with which once-wavering Democrats unified behind a formal impeachment probe — and the continuing divisions among them on how it should be conducted.

According to the Democrats, many of whom spoke on the condition of anonymity to describe private conversations, the House Judiciary Committee will continue playing the lead role in the proceedings, despite the desire of some Democrats to involve a broader swath of lawmakers and to at least partly sideline Rep. Jerrold Nadler (D-N.Y.), the panel’s fervently pro-impeachment chairman.

In the days leading up to Tuesday’s announcement, Pelosi explored potentially establishing a special “select” committee, with members handpicked by House leaders, but backed away from that idea after the dispute generated protests from liberals and threatened to divide the caucus along ideological lines.

Here's how house and senate democrats responded this week to the developments in the whistleblower case and the momentum toward impeachment. (The Washington Post)

Meanwhile, an even more fundamental dispute lingered — one that may not be resolved any time soon. Many Democrats are urging that the inquiry focus solely on the present outcry — Trump’s apparent admission that he urged Ukrainian President Volodymyr Zelensky to look for wrongdoing by the son of former vice president Joe Biden while withholding delivery of U.S. foreign aid — and not on other alleged abuses, such as the potential obstruction of justice detailed by Robert S. Mueller III as special counsel, episodes of congressional stonewalling and instances of bigotry.

More than 30 Democratic lawmakers announced support for impeachment just this week, many of them Democratic “frontliners” in vulnerable districts who said that the Ukraine allegations prompted them to speak out. Several said in interviews that the unique nature of the alleged episode — and the fact that it dealt squarely with Trump’s conduct as president and national security — counseled for it to be handled on its own.

“This should be a very distinct procedure relative to this allegation, rather than the whole basket,” said Rep. Dean Phillips (D-Minn.), a freshman who backed impeachment proceedings Monday after months of resisting pressure to take that step. “A lot of independents and a lot of Republicans are very like-minded, in particular, relative to this specific instance. And that’s why I think we’re looking at this so differently.”

But Pelosi’s involvement of other committees besides the Judiciary, Foreign Affairs and Intelligence panels with direct jurisdiction over the Ukraine matter suggest the impeachment brief could go much wider. The Financial Services Committee, for instance, is probing Trump’s real estate dealings; the Ways and Means Committee is seeking Trump’s tax returns; and the Oversight and Reform Committee is investigating whether Trump is using the presidency for self-enrichment.

“I see the most recent issue as one issue among many issues,” said Rep. Al Green (D-Tex.), who has pushed for Trump’s impeachment for two years, forcing multiple unsuccessful votes on removing Trump over alleged instances of bigotry. “All of the issues stacked on top of each other constitute a reason for why this issue is receiving the prominence and importance it’s receiving.”

The past two presidential impeachment processes, involving Richard M. Nixon and Bill Clinton, included votes of the full House authorizing the Judiciary Committee to formally investigate. There are no plans for such a vote now, and it is unclear to what degree Pelosi’s declaration on Tuesday formally changes the House’s posture.

That is a question likely to be litigated in the courts. The House has already cited the potential for impeachment in a lawsuit filed in July seeking disclosure of grand jury testimony gathered in the course of Mueller’s investigation. The Justice Department opposed that request in a legal brief filed this month that cited inconsistent statements from Pelosi, Nadler, House Majority Leader Steny H. Hoyer (D-Md.) and others regarding whether Democrats were actually pursuing impeachment.

Jonathan Turley, a George Washington University constitutional law professor who has been critical of the impeachment push, said Pelosi’s conclusive statement Tuesday could help the House prevail in that case, but said there are “still glaring contradictions” in the Democratic position.

“It would be much more convincing if the House was seeking a vote to dedicate this controversy to the Judiciary Committee for an impeachment inquiry,” he said. “This entire process has been uncomfortably casual — casual to the point of conversational in terms of the steps taken towards impeachment.”

For now, House vote or not, the Judiciary Committee will remain in the driver’s seat — putting Nadler in the role that Rep. Peter W. Rodino (D-N.J.) had with Nixon and Rep. Henry Hyde (R-Ill.) with Clinton.

Elsewhere in the House Democratic Caucus, there is concern — if not consternation — at how the panel has so far handled its investigations, which have largely been stonewalled by the Trump administration. Aside from the July appearance of Mueller, the panel has struggled to focus national attention on Trump’s conduct.

A hearing last week featuring former Trump campaign manager Corey Lewandowski devolved into a partisan exercise mostly notable for Lewandowski’s persistent and occasionally flamboyant refusals to answer Democratic questions. That changed during the hearing’s final moments, when a committee lawyer succeeded in getting Lewandowski to confirm allegations of potential obstruction by the president.

The relationship between Pelosi, a longtime impeachment skeptic, and Nadler has been tense in recent weeks, as the chairman urged the speaker to embrace impeachment proceedings. For months Pelosi refused, even as she signed off on the committee’s work and legal arguments suggesting that an impeachment inquiry was already underway.

Some members, in private conversations, urged Pelosi to find a more significant role for Rep. Adam B. Schiff (D-Calif.), the leader of the Intelligence panel based on his committee’s jurisdiction of the intelligence matters at the center of the allegations about Trump and on his comparatively measured approach toward impeachment over the past months. Those private discussions, stretching from the weekend into Monday evening, prompted Pelosi to sound out members on what they thought about the idea.

A prominent leader of moderate Democrats, Rep. Stephanie Murphy of Florida, publicly backed the appointment of a select committee Tuesday “to immediately investigate abuse of executive power,” comparing it to the special Senate committee empaneled during Watergate.

But there was significant skepticism among liberal members, as well as among outside activist groups, that appointing a new committee would amount to anything more than a delaying tactic. Rep. Alexandria Ocasio-Cortez (D-N.Y.) tweeted on Tuesday morning that Democrats “don’t have the luxury of time” to set up another panel.

“Judiciary has been investigating& putting the pieces together for months,” Ocasio-Cortez wrote. “Impeachment belongs there. We must honor jurisdiction, historical precedent,& work done + allow Judiciary to move forward.”

Paul Kane contributed to this report.