The political spotlight focused brightest on reticent special counsel Robert S. Mueller III for nearly two years, his every legal move and court filing scrutinized by a country eager to decipher what the Russia investigation had uncovered about President Donald Trump.

But with Mueller’s work done, the question changes from what Mueller found to how much of it House Judiciary Chairman Jerrold Nadler and other lawmakers can make public.

The New York Democrat and others in Congress made clear — even before Attorney General William P. Barr gave Congress a four-page summary of Mueller’s principal conclusions — just how far they would go to get the full special counsel report and backing evidence.

[McConnell, Graham leave room for Barr to withhold parts of Mueller report]

“If it is not made public in its entirety, we will use a compulsory process, we’ll subpoena the report, and if necessary, we reserve the right to call Mueller before the committee, or maybe even Barr before the committee,” Nadler told NBC News on Friday, after Mueller submitted the report to the attorney general.

Such moves could set off a historic separation of powers battle between the legislative and executive branches that some lawmakers say might go all the way to the Supreme Court — particularly if Trump moves to block part of the release through a claim of executive privilege.

Also watch: Judiciary and oversight subpoena power, explained

One part of Barr’s summary Sunday, a quote from the Mueller report, appears to give Democrats a reason to push for more information: “The Special Counsel states that ‘while this report does not conclude that the President committed a crime, it also does not exonerate him.’”

Barr then wrote that he and Deputy Attorney General Rod Rosenstein concluded there was not enough evidence to establish Trump committed an obstruction-of-justice offense, in part because Mueller recognized that “the evidence does not establish that the President was not involved in an underlying crime related to Russian election interference.”

Nadler tweeted that it only took two days for Barr to conclude that there will be no Justice Department action and there must be “full transparency in what Mueller found that did not exonerate Trump.”

“But Special Counsel Mueller clearly and explicitly is not exonerating the President, and we must hear from AG Barr about his decision making and see all the underlying evidence for the American people to know all the facts,” the Judiciary chairman said. 

Much of what happens next depends on what Barr decides about how much of Mueller’s final report can be disclosed to Congress and the public. Barr told lawmakers Friday he remains “committed to as much transparency as possible.” Trump has called for the report to be released though he has not said if he would use executive privilege.

There are some parts of the report that could remain confidential, such as grand jury work products, classified information or evidence that is part of ongoing investigations, Delaware Democrat Chris Coons, a Senate Judiciary member, said Saturday.

But there are signs other parts of the report could be withheld.

Barr told the Senate during his confirmation hearing this year that Justice Department policy is to not release derogatory investigative information about people who are not charged with a crime. Trump has not been indicted by Mueller’s office, and DOJ officials told reporters there are no more special counsel indictments coming.

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Pair that with a decades-old internal Justice Department legal opinion, never tested in court, that a sitting president cannot be indicted, and Democratic lawmakers fear it is a loophole the administration could exploit to keep information on Trump from the public.

Additionally, Trump hired lawyers to aggressively invoke executive privilege to resist the release of details describing confidential and sensitive communications between the president and his senior aides, if there are any in the report, The Washington Post reported in January.

“Ultimately, if the administration tries to hide the full Mueller report, the president will find himself relying on the courts to quash a congressional subpoena,” Vermont Democrat Patrick J. Leahy, also a Senate Judiciary member, wrote in a Washington Post op-ed published Friday night.

Leahy highlighted the parallels to the Supreme Court’s decision in United States v. Richard Nixon, the 1974 case in which the president lost his fight to keep secret White House recordings. But he added, “No one can predict with certainty what the courts will do.”

Coons told reporters Saturday that a consistent concern for him during confirmation hearings for Trump’s two Supreme Court picks, Justices Neil M. Gorsuch and Brett M. Kavanaugh, was the “very broad view they have of executive power.” And that could favor the president’s chances in court.

“I think it should be prevented from use as a shield for potentially inappropriate or even arguably illegal activity in the executive branch,” Coons said. “I am concerned that executive privilege might be broadly asserted here, and that that might end up shielding from view some of the most important conclusions of the Mueller report.”

[Meet Jerry Nadler, the Next House Judiciary Chairman and Trump’s New Enemy No. 1]

Nadler has said that executive privilege cannot hide misconduct, and that the president waived privilege when he gave documents to investigators.

On Sunday before the release of Barr’s conclusions, Nadler told CNN he is “absolutely” willing to pursue a subpoena all the way to the Supreme Court. And when pressed about how long he would wait for the Justice Department to turn over the report, Nadler replied, “It won’t be months.”

He was among the House committee chairs who spoke on an emergency Democratic Caucus conference call Saturday, and reiterated that the report should be released to Congress so that further oversight and legislation can be completed if the issues raised in the report so warrant, according to a person on the call.

The chairs told Democratic members that releasing the full report is supported by past precedent and the Department of Justice’s recent practice of releasing investigative documents in matters of critical public interest, the person said.

And on the call, Speaker Nancy Pelosi said she would reject any classified briefing so members can talk publicly about what they learn.

Barr, in his letter Sunday, wrote that once information related to the grand jury and other investigations is taken out, he “will be in a position to move forward expeditiously in determining what can be released in light of applicable law, regulations, and Departmental policies.”