This week’s congressional hearings with Robert Mueller will air “very substantial evidence” of wrongdoing by US President Donald Trump and make a public case for impeachment, the House Judiciary Committee chairman has said.

And Republicans have pledged sharp questioning of the former special counsel about what they see as a “one-sided” Russia investigation.

Days before back-to-back hearings on Wednesday, both sides seemed to agree that Mr Mueller’s testimony could be pivotal in shifting public opinion on the question of “holding the president accountable.”

Jerrold Nadler
Jerrold Nadler will chair one of the committees to question Robert Mueller on Wednesday (J Scott Applewhite/AP)

“This is a president who has violated the law six ways from Sunday,” said the committee’s chairman, Representative Jerrold Nadler.

The New York Democrat argued that Mr Mueller’s report lays out “very substantial evidence” that Trump is guilty of “high crimes and misdemeanors”, the constitutional standard for impeachment.

Mr Nadler said: “We have to present — or let Mueller present — those facts to the American people … because the administration must be held accountable and no president can be above the law.”

The House Judiciary Committee and the House Intelligence Committee will question Mr Mueller in separate hearings on his 448-page report released in April.

While the report did not find sufficient evidence to establish charges of criminal conspiracy between the Trump campaign and Russia to swing the election, it said Mr Trump could not be cleared of trying to obstruct the investigation.

But Mr Mueller believed Mr Trump couldn’t be indicted in part because of a Justice Department opinion against prosecuting a sitting president.

Mr Mueller has said he doesn’t intend to speak beyond the findings of the report in congressional hearings.

Still, Democrats on the Judiciary Committee plan to focus on a narrow set of episodes laid out in the report to direct Americans’ attention to what they see as the most egregious examples of the president’s conduct, which point to obstruction of justice.

The examples include Mr Trump’s directions to then-White House counsel Donald McGahn to have Mr Mueller removed and, later, orders from Mr Trump to Mr McGahn to deny that happened.

Democrats also will focus questioning on a series of meetings Mr Trump had with former campaign manager Corey Lewandowski in which the Republican president directed Mr Lewandowski to persuade then-Attorney General Jeff Sessions to limit Mr Mueller’s investigation.

Georgia Representative Doug Collins, the top Republican on the committee, argued that “any thought of impeachment is waning” and that the American public has moved on.

He added that Republicans will be focused in their questioning on making clear that the Mueller report represents a “final episode” in the Russia probe, which he described as flawed.

“Remember, the Mueller report is a one-sided report. It has not been questioned from the other side. This is our chance to do that,” Mr Collins said.

Mr Mueller’s appearance comes more than two years since the start of the Russia investigation, an extraordinary moment in the Trump presidency when, after Mr Trump had fired FBI Director James Comey, his Justice Department appointed Mr Mueller to take over the inquiry into election interference and the potential role that Mr Trump and his winning 2016 campaign may have played.

While Mr Mueller’s testimony was once envisioned as a crystalizing event – a Watergate-style moment to uncover truths – public attention has drifted in the months since the report was released.