WASHINGTON – After the release seven weeks ago of special counsel Robert Mueller's report, House Democrats demanded millions of pages of evidence they said were crucial to understanding both Russian election meddling and the president's conduct.

The House Judiciary Committee scheduled a hearing to question Attorney General William Barr, who blacked out portions of the report. Democrats subpoenaed former White House counsel Don McGahn, a key figure who described President Donald Trump's potential obstruction of justice, for another hearing. And they've negotiated with Mueller himself to testify so Americans could hear directly from the people involved.

After all that, the committee will hear from its first witnesses Monday: a panel of cable television regulars who weren't.

So far, nearly every attempt by House Democrats to air evidence about Trump's conduct during the investigation that shadowed his presidency has run – for now, at least – into a wall. Barr refused to appear and defied a subpoena to provide Congress the full report. McGahn defied his subpoena under a White House claim of executive privilege, as have other former aides who spoke to investigators about the president's actions. And Mueller said the report should speak for itself.

House Democrats have launched a series of wide-ranging probes of Trump and his administration, and the pace of those inquiries has sparked complaints from his fiercest critics and his most stalwart allies. A growing faction of 59 lawmakers urged a start to impeachment proceedings. House Republicans, who note Mueller found no conspiracy between the Trump campaign and Russia, have said they should already be over.

"There's been no evidence that would necessitate an impeachment,” House Minority Whip Steve Scalise, R-La., said Wednesday.

House Speaker Nancy Pelosi of California insists that Democrats have a plan to build a case against the president and that they are pursuing it methodically. The Judiciary Committee has held Barr in contempt. The full House will vote Tuesday to authorize the panel to ask a federal court to enforce the subpoenas against Barr and McGahn. Two federal judges have already upheld subpoenas for Trump's financial documents, although the president appealed.

“We know exactly what actions we need to take and while that may take more time than some people want it to take, I respect their impatience," Pelosi said Wednesday. Whether that plan ends in impeachment or not, she said, the six committees investigating Trump should gather evidence to build the strongest possible case against Trump. With Mueller's criminal inquiry over, the investigations of Trump have entered a new and decidedly more political phase approaching the 2020 election.

Trump has blasted the multiple inquiries as partisan harassment and threatened to defy all subpoenas. House Minority Leader Kevin McCarthy, R-Calif., said Tuesday that Democrats had a plan long before they reclaimed the House in January to impeach Trump. "They only care about politics," he said.

But that resistance may only have intensified Democrats' frustration and added to calls for more dramatic steps.

“It’s basically painting Congress in a corner so that the only answer that they’ll have to his stonewalling and his breaking of norms is to open up impeachment proceedings,” said Kent Greenfield, law professor at Boston College and former clerk for Supreme Court Justice David Souter. “The education function is crucial to shore up the Democrats’ view and argument next year that the president is unfit and isn’t taking the job seriously.”

Experts said there are risks for Democrats, too. Testimony from McGahn and other officials would let Americans hear about Trump's conduct from people who witnessed it. But if the probes don't turn up compelling evidence that people can see for themselves, voters could have questions about whether the investigations were worthwhile or legitimate.

"I see tension over the desire to seek impeachment, but the concern is that if it comes to nothing and then serves only to energize the base that supported Trump," said John Marston, a former federal prosecutor and now a partner at Foley Hoag. "Revealing facts and evidence that show what you're doing actually makes sense and is not just political – and is legitimate."

Hearings to explain Mueller report

Mueller said May 29 that his 448-page report should speak for itself and his testimony isn’t necessary. But Democrats are eager to question him and may subpoena him, even if Mueller sticks to simply reading from the text.

Unable so far to obtain testimony from key figures in Mueller's investigation, House Democrats will begin a series of hearings this week with stand-ins to illustrate its findings. The House Judiciary Committee on Monday will feature John Dean, a former White House counsel who testified to the Senate in June 1973 about the Watergate cover-up under President Richard Nixon.

Judiciary Chairman Jerry Nadler, D-N.Y., said Monday's hearing is meant to analyze episodes of possible obstruction in the Mueller report.

“I think John Dean is definitely theater,” said Thomas Alan Schwartz, a professor history and political science at Vanderbilt University. “On the other hand, I think this is part of a larger attempt to create a specter or aura around Donald Trump as you move into 2020 that would contribute to his political defeat.”

But Greenfield said Dean’s appearance could demonstrate how a White House counsel could testify if he felt the president was engaged in wrongdoing. The Mueller report described Trump repeatedly asking McGahn to remove Mueller, which legal experts have said is one of the strongest episodes of possible obstruction. McGahn defied his subpoena at the request of White House lawyers who argued that his conversations with Trump should remain secret under executive privilege, to ensure the president gets candid advice from aides.

“It’s hard to say that Don McGahn is protected by executive privilege if John Dean wasn’t,” Greenfield said.

The House Intelligence Committee also plans a series of hearings about Russian interference in the 2016 election, to explain the difference between counterintelligence and criminal investigations. A hearing Wednesday will feature Stephanie Douglas and Robert Anderson, who are each former executive assistant directors of the national security branch of the Federal Bureau of Investigation.

Chairman Adam Schiff, D-Calif., has focused on Trump’s exposure to foreign influence for negotiating a real-estate deal in Russia during the campaign. Trump’s former personal lawyer Michael Cohen has been imprisoned for charges that include lying about the project to Congress.

Trump has called Cohen's testimony "shameful" and argued that the real-estate negotiations weren’t a crime because he was in business while campaigning, and that the talks continued because he might have lost the election.

Some Democrats have complained that the process is moving too slowly, but haste carries other risks.

“They may certainly be frustrated in part because they may feel that the clock is running out on them,” said Costas Panagopoulos, a political-science professor at Northeastern University. “Part of this is politics and gamesmanship. But part is also the genuine reluctance on the part of the speaker to move in a direction that could backfire on the party or put the country through a very, very difficult process.”

Court fights over subpoenas

The House scheduled a vote Tuesday to authorize the Judiciary Committee to enforce subpoenas to Barr for the unredacted Mueller report and millions of pages in underlying evidence, and to McGahn.

The Justice Department offered last week to resume negotiations to release more documents associated with the report, but only if the committee revoked its contempt threat, which Nadler declined. Rep. Doug Collins of Georgia, the top Republican on the committee, said the panel has made unreasonable demands.

“When Judiciary Democrats wield subpoena power like a sword instead of a plow, their investigations bear little fruit,” Collins said.

Trump has already sued to block subpoenas for his financial records. Two federal courts sided with lawmakers, saying their demands were legitimate. Trump has appealed both decisions, a process likely to stretch at least through the summer.

In another matter headed for litigation, Oversight Chairman Elijah Cummings, D-Md., said the panel will vote this week on whether to hold Barr and Commerce Secretary Wilbur Ross in contempt for defying a subpoena for documents about a citizenship question added to the 2020 Census.

The legal process is unlikely to be speedy, but it comes with its own political benefits.

“The name of the game is not speed,” Greenfield said. “The name of the game is to win a series of news cycles between now and November 2020.”

More on President Donald Trump's conflicts with Congress:

'Slow-motion constitutional car crash': Trump, Congress battle over investigations with no end in sight

'We're fighting all the subpoenas.' Congress and Trump prepare to battle over wide-ranging probes

Robert Mueller, in first public remarks, says charging Trump was 'not an option we could consider'