– Many Democrats conceded Monday that the possibility of impeachment proceedings against President Donald Trump is over, at least for now — marking a dramatic retreat in the wake of the conclusion by special counsel Robert Mueller that Trump's campaign did not conspire with Russia in the 2016 election.

Instead, Democrats immediately began focusing on a narrower debate over the Attorney General William Barr's decision that Trump should not face any charges related to obstruction of justice in his attempts to impede the Russia probe. Mueller's conclusions on the Russia investigation, and Barr's related decision to not prosecute possible obstruction, further diminished the hopes of some on the left that Trump might be vulnerable to impeachment for crimes related to Russian election interference.

In addition to growing skepticism among House Democrats, two key centrist Republican senators, Susan Collins of Maine and Mitt Romney of Utah, also said Monday that any talk of impeachment should now be off the table.

House Speaker Nancy Pelosi, D-Calif., had already declared earlier this month that she was against impeachment without bipartisan support. The new developments leave her with the task of managing less ambitious efforts by Democrats to both hold the president accountable and provide fodder for candidates vying to challenge him in 2020.

Some House Democrats suggested Monday that they will double down on a strategy of attempting to cripple Trump with what one aide described as "a thousand cuts" — highlighting what Democrats view as Trump's abuse of his office as well as policies that repel voters, like family separations at the border.

But Democrats will also have to grapple with fresh criticism from the White House and Republicans about their previous rhetoric on Trump and Russia, including claims that may appear exaggerated or overblown in the wake of Mueller's report, though its details have not been released publicly.

The decision to focus on Barr is a conscious one, Democrats said. During a Sunday phone call with Pelosi and other House chairmen, Judiciary Committee leader Jerrold Nadler, D-N.Y., argued that Barr, rather than Mueller, should be their most immediate target in the aftermath of the Russia probe's conclusions.

Within hours of the call, House Democrats began a concerted effort to accuse Barr of bias and protecting the president. Nadler and other House chairmen said in a statement that a summary of Mueller's findings provided to Congress by Barr "may be a partisan interpretation of the facts." Other Democrats pointed to a 2018 letter Barr wrote, arguing that the president could not obstruct justice, suggesting that Trump chose him to lead the department to shield himself from accountability.

"You've got to question the appointment from jump street," said House Judiciary Committee member Steve Cohen, D-Tenn., comparing Barr to Trump's former lawyer and fixer Roy Cohn. "Trump was looking for a Roy Cohn, and that's not something the public wants to be their attorney general or making objective decisions. … They were never going to indict him."

Over the past year, Chairman Adam Schiff, D-Calif., and other Democrats on the House Intelligence Committee have repeatedly declared that they have seen evidence of collusion between the Trump campaign and Moscow. On Sunday, for example, Schiff reiterated that message on ABC's "This Week," just hours before Barr's summary of Mueller's findings was released, listing "secret meetings in Trump Tower" and other controversial episodes as examples.

But Mueller's findings have called those allegations — and claims of evidence — into question. Barr's summary repeatedly stated that Mueller had not determined that Trump or any of his subordinates coordinated or collaborated with Russian officials to sway the 2016 election.

The discrepancies have led top Republicans — from White House official Kellyanne Conway to House Minority Leader Kevin McCarthy, R-Calif. — to call for Schiff's resignation from the panel.

"He ought to resign today," Conway said of Schiff on "Fox and Friends" on Monday. "He's been on every TV show 50 times a day for practically the last two years, promising Americans that this president would either be impeached or indicted."

Democrats on the intelligence panel are refusing to back down. Even before Barr released Mueller's findings, Schiff had argued that a lack of charges would not mean there wasn't "compelling and incriminating evidence" of collusion that the American public deserved to see.

"Our probe in intelligence is much broader than the scope of what special counsel Mueller had to deal with," said Rep. Raja Krishnamoorthi, D-Ill., arguing that he did not believe Mueller focused on all the counterintelligence the House panel is trying to scrutinize.

In another sign of the effect of Mueller's report, the House Intelligence panel announced Monday that it was postponing a Wednesday hearing with former Trump business associate Felix Sater about his plans to build a Trump Tower in Moscow — one of the key events Democrats say fell outside the purview of Mueller's probe.

In the meantime, no one on Capitol Hill yet knows whether Mueller's full report will be released. At no point in his letter did Barr indicate that he intended to transmit the full report to Congress.

"There's nothing here that makes a commitment to deliver the full report. He's never made that commitment," Sen. Richard Blumenthal, D-Conn., said in an interview. "That is a highly significant omission."

Given Pelosi's precondition of bipartisan support for impeachment proceedings, Mueller's findings have made that a moot point. Some of Trump's staunchest critics among congressional Republicans said Monday that they consider the Russia matter closed as a line of inquiry that would lead to anything close to impeachment.

"Certainly with regards to Russia, interference or collaboration with the Trump campaign or the president himself, that issue is taken off the table," Romney, who led a brief anti-Trump insurgency in 2016, told reporters Monday.

Romney, the party's 2012 presidential nominee and frequent recipient of Trump barbs, said he agreed with Barr's findings that the obstruction of justice charge was pointless.

"The attorney general pointed out the obvious, which is, if there's no underlying crime, it's very difficult to make a case for an obstruction of justice looking into the absence of a crime," Romney said.

Collins said that she wants to know more about the obstruction issues but that Mueller is "so experienced and he conducted such an extensive, in-depth investigation" that his inconclusive finding spoke for itself.

"If he had found the evidence to sustain an obstruction charge, I'm sure he would have said that," Collins said.

Democrats seem intent on focusing their frustration on Barr. Nadler and other Democratic chairman criticized the attorney general for taking less than 48 hours to determine a difficult obstruction question that Mueller couldn't resolve in 22 months of investigating.

"That's a little bit of a rush to judgment from a guy who has made it very clear that he wanted that job to protect the president," said Judiciary panel member David Cicilline, D-R.I.