US president Donald Trump’s intervention into a criminal case connected to his own conduct has drawn fierce rebukes from Democrats and a few Republicans amid calls for an investigation.

Mr Trump defied the conventions of his office to commute the sentence of political confidant Roger Stone, four months ahead of US election day.

The move came just days before Stone was due to report to prison to serve 40 months for crimes related to the Russian collusion investigation.

The White House confirmed the commuting of the sentence in a statement, saying Stone was a victim of the Russia “hoax”.

Though short of a full pardon, the commutation alarmed critics who have long been critical of the president’s repeated interventions in the nation’s justice system.

Stone had been sentenced in February for lying to Congress, witness tampering and obstructing the House investigation into whether the Trump campaign colluded with Russia to win the 2016 election.

Shortly before heading out for his Virginia golf club on Saturday morning, Mr Trump made unfounded accusations against his political foes while taking another swipe at special counsel Robert Mueller’s investigation, which led to convictions for six Trump aides or advisers – including Stone, a larger-than-life political character who embraced his reputation as a dirty trickster.

“Roger Stone was targeted by an illegal Witch Hunt that never should have taken place,” Mr Trump tweeted. “It is the other side that are criminals, including Biden and Obama, who spied on my campaign – AND GOT CAUGHT!”

Mr Trump has long sought vengeance against the Russia investigation that helped define his first two years in office.

He was sentenced as part of the probe into Russian interference
Stone was sentenced as part of the probe into Russian interference (Al Drago/AP)

Now that the coronavirus pandemic has imperilled his re-election chances by crushing the economy and sending his poll numbers sliding, he has taken to testing the limits of his power in order to reward loyalty and fire up his conservative base.

The decision to commute the sentence of the 67-year-old Stone was loudly celebrated by some in Mr Trump’s orbit as a triumph over deep state prosecutorial overreach.

But the move came over the advice of a number of the president’s senior advisers, who warned him it would be politically self-destructive to reward Stone for his silence.

Mr Trump had long floated the idea of clemency for Stone – as well as for other associates in legal trouble, including his former national security adviser Michael Flynn and campaign chairman Paul Manafort – which itself was viewed by some as witness tampering by encouraging them not to cooperate with prosecutors.

Nancy Pelosi
Nancy Pelosi (AP)

The reaction from Democrats was swift and furious.

US house speaker Nancy Pelosi called it “an act of staggering corruption”, saying legislation is needed to prevent an American president from pardoning or commuting the sentence of someone who acted to shield that president from prosecution.

House intelligence committee Chair Adam Schiff called it “offensive to the rule of law and principles of justice”.

And Mr Trump’s Democratic challenger, Joe Biden, resurfaced a 2019 tweet in which he said that “Trump has surrounded himself with people who flout our laws – we shouldn’t be surprised that he thinks he is above the law”. Mr Biden added: “Still true.”

Republicans largely stayed silent on the issue on Saturday, reluctant again to challenge a president who remains very popular with rank-and-file voters. However, one loud voice was Utah senator Mitt Romney, who was also the lone Republican senator to vote to convict the president during his impeachment trial earlier this year.

Mr Romney tweeted: “Unprecedented, historic corruption: an American president commutes the sentence of a person convicted by a jury of lying to shield that very president.”

Senator Pat Toomey, a Pennsylvania Republican, signalled dismay with the commutation, saying in a statement that it was a mistake while calling the Russia investigation “badly flawed” and a source of “frustration”.

He added that Stone had been duly convicted and that any objections to the conviction and trial “should be resolved through the appeals process”.

Mark Sanford, the former South Carolina congressman who made a short-lived primary challenge to Trump, wrote: “So much for the Republican Party being the party of law and order. Have we not lost our minds in not condemning as a party the president’s corruption by Roger Stone.”

But most of Republicans who did speak out about the decision supported it. Senator Lindsey Graham, a Trump confidant, said Stone was convicted of a “non-violent, first-time offence” and the president was “justified” in commuting the sentence.

Mr Trump likely cannot afford more political damage. He is trailing Joe Biden – according to his campaign’s own private admissions – and his effort to reboot his re-election bid took another blow when a planned rally for Saturday night in New Hampshire was postponed.