An explosive atmosphere is brewing in the US after Special Counsel Robert Mueller submitted his report on whether President Trump had benefited from Russian help in winning the 2016 election and whether he was guilty of obstructing justice. On May 1, during Attorney General William Barr's testimony to the senate judiciary committee, some Democratic members of the committee tore into him to expose lies he told about Mueller's conclusion. His conduct clearly showed that he was acting as Trump's counsel and surrogate rather than impartially discharging the duty of AG.

The situation had already become tense and confrontational as Trump embarked on a fraught path of challenging the oversight role that the constitution confers on the Congress. He has blocked a number of subpoenas the Congress issued to some members of his staff. He asked those called for interrogation to defy the summons.

A pivotal figure in the battle is Donald McGahn, former Trump Counsel. He defied an order from Trump to fire Mueller and thus pre-empt the investigation. McGahn also said that the president told him to deny the episode ever occurred. In other words, the president first tried to block the investigation, and failing, he tried to get McGahn to say he made no such obstruction attempt. McGahn finally resigned.

The Congress is resolved to get at the truth, and establish clearly, for the American people, whether or not the president committed a serious misdemeanour unbecoming of a president. Legal experts say Trump's defiant action could face obstacles. The House has the option of holding in contempt those Trump officials who have refused to comply with the summons. It can ask judges to order compliance.

On Trump's defiance of the congressional oversight, it is hard to disagree with the observation of the House Judiciary committee chairman Jerold Nadler that it is an attempt to "render Congress inert as a separate and co-equal branch of the government. If the Congress does not stand up, it will never be able to stand up to any president in future." He said that, "the very system of the government of America…the system of not having a president as a dictator—is very much at stake."

Nadler's views are very similar to what the Washington Post and the Economist magazine said. The Washington Post in an op-ed by its editorial board observed: "Sorry Mr President, Congress has every right to investigate you." The paper says that "absent very strong countervailing considerations—stronger than those the administration asserted in this case—Congress is generally entitled to disclosure."

The Economist magazine more or less echoes the same view: "The author of the constitution made it clear that Congress has the task of dealing with a rogue president."

On congressional oversight, normally the American presidents have taken the approach of negotiations and accommodation, consenting to investigation demands which are seen to have a clear and compelling logic.

In this febrile situation, talk about impeachment has acquired some momentum after Barr's disastrous performance in the senate hearing. At this point 56 percent of Americans are against impeachment, and 37 percent are for. In any case, with the pliant and totally submissive Republicans controlling the Senate, even if the House impeaches the president, he cannot be removed from office. As the current fight evolves it is quite possible that the public sentiment on impeachment question could change.

Senator Elizabeth Warren called for Trump's impeachment sometime back. Now on April 30, Joe Biden has also said that "if the administration blocks the (congressional) investigation, they have no alternative but to go to the only other constitutional resort which is impeachment."

Some important things that happened during Barr's hearing in the senate judiciary committee needs to be briefly stated. The most serious revelation, and something that destroyed the Attorney General's trustworthiness, was that the Democratic members revealed to the American people that Barr was trying to portray a false picture about the president's conduct. He purposely held back Mueller's executive summary, and created his own summary different from Mueller's. His whole thrust was to clear the president.

A second notable thing is that the Republican Chairman of the committee Lindsay Graham's contention in opening statement set a brazenly partisan tone. His remark that "the President never did anything to stop Mueller from doing his job" stands in stark contrast to the reality.

On Barr's wishy-washy replies to questions, Vermont senator Patrick Leahy accused him of "purposely misleading". Senator Sheldon Whitehouse (D) Rhode Island blurted out: "I mean, boy! That's some masterful hairsplitting." And Barr equivocated when Kamala Harris, a presidential candidate and an ex-attorney general of California asked if the president or anyone in the White House had asked or suggested that he open an investigation on any one. "Yes or no?" she pursued as if she was interrogating a shoplifter.

On the question of whether on Russian collusion Mueller exonerated Trump, the fact is that Mueller revealed a lot of episodes of Trump's campaign people like Paul Manafort and Carter Page having made contacts with Russians. While the president is not directly incriminated, the political implications for him is quite troubling.

On obstruction of justice issue, the following things investigated by Mueller matter profoundly:

i)    Trump's wish to fire Mueller.

ii)   Trump's sacking of FBI Director James Comey.

iii)  His order to the White House counsel McGahn to deny that Trump had wanted to fire Mueller.

Barr was called for interrogation by the House judiciary committee on Thursday May 2 but he didn't turn up. Congress is weighing the option of holding him in contempt.

What is the legal basis of this congressional tool? It is not a constitutional provision. However, in 1821, the Supreme Court said that without the power to hold people in contempt of Congress, the legislative branch would "be exposed to every indignity, and interruption that rudeness, caprice, or even conspiracy may mediate against it." So Congress stands on solid ground if it moves a contempt motion.

Trump has adamantly resisted attempts to keep a lot of personal issues hidden from public view: like his financial affairs. There is now a sense that the discussion on the Mueller report and interrogation of Barr in senate is making the dam leak. When Mueller testifies to Congress in a few days, it will be a blockbuster moment. It is possible that what comes out of the Mueller hearing will have a significant impact on public sentiments, and could even be a tipping point.

Ziaus Shams Chowdhury is a former ambassador.