Washington (CNN) Vladimir Putin keeps on getting the last laugh, and he knows it.

The Russian leader and former KGB officer could not resist some sardonic trolling on a day when the tortured legacy of the 2016 election sowed fresh mistrust and discord in Washington and the US President's eldest son, Donald Trump Jr. , got caught in the fallout.

"Despite the exotic nature of the work of special counsel Mueller, we must give him credit," Putin said during a visit from US Secretary of State Mike Pompeo in Sochi on the Black Sea.

Emulating President Donald Trump's own language, the architect of Russia's election meddling operation said Mueller's report showed claims of collusion were "nonsense," appearing to be only too happy to add to the fog of controversy churning over the former FBI director's conclusions.

Trump claims he was "exonerated" by Mueller. But while the special counsel did not establish a conspiracy between Trump's team and Russia, he did unveil multiple contacts between the two sides in his report . And while deciding not to reach a decision on whether Trump obstructed justice, he piled up evidence that more than 800 former federal prosecutors said could lead to a prosecution of Trump were he not president.

Some 5,500 miles west of Putin, the still bitter reverberations of that divisive election tightened their corrosive grip over the institutions of US political life.

Taking a break from worrying about a trade war with China and a possible slide to war with Iran, Washington plunged back into disputes raging in the aftermath of the Mueller endgame.

Trump's team and Democrats are now fighting a war of attrition over Trump's personal finances, campaign and presidency that was born from the Russia intrigue and will further strain national unity.

Which is presumably fine by Putin, since Mueller concluded Russia's nefarious efforts were designed to "provoke and amplify political and social discord in the United States."

In one of Tuesday's most striking developments, sources told CNN that Attorney General William Barr is now working with the CIA and FBI leadership to probe the origins of FBI surveillance against Trump's campaign. An investigation into the same area by the Justice Department's Inspector General is also under way.

"But I think it's a great thing that he did it," Trump said.

"I saw it last night and they want to look at how that whole hoax got started. You know what? I am so proud of our attorney general, that he is looking into it. I think it's great," he added.

The President's comment will do nothing to ease the impression among Democrats that Barr, who rolled out the Mueller report in a favorable manner for Trump, is acting less as America's top law enforcement officer than the President's personal attorney.

Trump has burned through the hierarchy of top Justice Department officials at an alarming rate, and there were signs Tuesday that FBI Director Christopher Wray could be on thin ice.

Trump was objected to Wray's refusal to adopt Barr's term -- "spying" -- for warrant approved surveillance of his campaign.

"I certainly didn't understand that answer. I thought it was a ridiculous answer," Trump told reporters.

Breakthrough on Don Jr.

JUST WATCHED Trump Jr. reaches deal with Senate committee to testify Replay More Videos ... MUST WATCH Trump Jr. reaches deal with Senate committee to testify 01:46

In another bitter front of the Russia drama, there was a tentative breakthrough.

Trump Jr. and the Senate Intelligence Committee brokered a deal for him to return for a closed-doors testimony in mid-June.

The agreement comes after the committee issued a subpoena last month that sparked intense conservative blowback against the Republican committee chairman, Sen. Richard Burr of North Carolina.

CNN's Kara Scannell reported the impasse ended when the committee agreed to limit the scope and duration of the interview.

The appearance will last between two and four hours and be limited in scope to five or six topics. But questions about the June 2016 Trump Tower meeting and the Trump Tower Moscow project will not be off limits, said two sources familiar with the matter.

It was the kind of compromise that offers something to both sides, and was a rare exception in today's Washington.

The President had earlier complained his son was being victimized, by a rare committee led by a Republican to put pressure on Trump's inner circle.

"My son spent, I guess, over 20 hours testifying about something that Mueller said was 100% OK. And now they want him to testify again ... I have no idea why, but it seems very unfair to me," Trump said.

The deal did little to cool tensions on Capitol Hill.

Some Democrats immediately demanded more cooperation from Trump world, given the multi-front showdown over testimony and documents that has several cabinet officers facing a possible contempt of Congress vote by the full House.

"It's about time that somebody from this administration or associated with this President is coming in freely," Rep. Jimmy Gomez, a California Democrat, told CNN's Wolf Blitzer.

"I just wish they would do this across the board. This administration had one strategy, which is dodge, delay and lie to protect this President."

Yet another development in the Russia drama Tuesday brought potentially troubling omens for the administration.

A federal judge in Washington cast doubt on the notion that the courts could limit Congress' ability to investigate Trump, in the first major hearing over congressional subpoenas for records from the President's accounting firm.

"Am I right, there isn't a single Supreme Court case or appellate case since 1880 that has found a congressional subpoena overstepped its bounds?" Judge Amit Mehta asked Trump's lawyer. "I agree there are outer limits, but it's not clear to me what they are."

Mehta said he would not rule on the subpoena this week.

Mehta also noted how Congress has done historically important work with investigations in the past, like in the Watergate and Whitewater investigations.

His comments were an early sign that the judicial branch could seek to side with the legislative branch as it faces multiple demands to referee Congress's showdown with the White House.

Another legal wrangle intensified when it emerged Tuesday that the House Intelligence Committee is investigating whether attorneys representing Trump, his family and the Trump Organization misled the committee or obstructed its Russia investigation.

The case arises from the a false statement to Congress in 2017 by Trump's now jailed former personal attorney Michael Cohen, according to letters obtained by CNN.

House Intelligence Committee Chairman Adam Schiff warned that if any individual is allowed to lie to the committee, others could be encouraged to do so.

Trump's lawyers argue that Schiff's document request would force them to violate attorney-client privilege.

No more meddling

JUST WATCHED Pompeo prepares to meet Putin after Mueller report Replay More Videos ... MUST WATCH Pompeo prepares to meet Putin after Mueller report 01:33

Back on the Caucasian Riviera, Pompeo brought up the question of election meddling directly with the Russians -- with unusual clarity.

"I made clear to Foreign Minister (Sergey) Lavrov, as we've made clear for the past months, that interference in American elections is unacceptable," Pompeo said.

"If the Russians were engaged in that in 2020, it would put our relationship in an even worse place than it has been, and I encouraged them not to do that, that we would not tolerate that," he said.

Putin's comment contrasted with Trump's still mystifying failure to publicly accept that election meddling happened or to confront Putin in any way about it.

The reality of what happened in 2016 became even more clear on Tuesday as a Trump ally, Florida Gov. Ron DeSantis, revealed that a second county in the state had been hacked.

But he added that there was no manipulation of data and said the the intrusion "had no effect" on Florida vote totals. He did not identify the counties involved.