Top advisers to then-president Donald Trump told him that his claims of widespread election fraud were unfounded and would not reverse his 2020 election loss, but he refused to listen, according to testimony at a hearing of the committee investigating the January 6, 2021, riot at the US Capitol.

Close aides and family members said they told Trump that they found no merit in a wide range of often outlandish allegations that surfaced after his election defeat, including reports of a “suspicious suitcase” containing fake ballots, a truck transporting ballots to Pennsylvania and computer chips swapped into voting machines.

“I thought, boy, if he really believes this stuff he has lost contact with, he’s become detached from reality,” said William Barr, who served as Trump’s attorney-general and was long known as loyal to the Republican president. 

In video testimony, Barr bluntly dismissed claims of fraud as “bullshit” and “crazy stuff”.

“There was never an indication of interest in what the actual facts were,” he said on Monday.

The Democratic-led House of Representatives Select Committee investigating the assault on the US Capitol by thousands of Trump supporters presented its findings at the second of an expected six this month on its nearly year-long investigation into the riot.

Monday’s hearing sought to make the case that Trump ignored the advice of many of his own staffers when he claimed that the 2020 presidential election was “stolen” from him.

Committee members argue that Trump’s repeated fraud claims, known by Democrats as “The Big Lie”, convinced his followers to attack the Capitol.

“He and his closest advisers knew those claims were false, but they continued to peddle them anyway, right up until the moments before a mob of Trump supporters attacked the Capitol,”  Democratic Representative Zoe Lofgren said.

Democrats said Trump raised some $US250 million from supporters to advance fraud claims in court but instead steered much of the money elsewhere.

“The ‘Big Lie’ was also a big ripoff,” Lofgren said.

Trump has denied wrongdoing, and repeatedly insisted he did not lose, dismissing the select committee investigation as a political witch hunt.

Opinion polls show many of Trump’s supporters still believe his false claims about the election. Some are running for offices in which they would oversee future elections. Trump has hinted at running for president again in 2024.

Bill Stepien, Trump’s campaign manager, said he recommended on election night that Trump steer clear of any pronouncement of victory and instead say votes were still being counted.

“He thought I was wrong. He told me so, and that they were going to go, that he was going to go in a different direction,” Stepien said in videotaped testimony. Stepien was slated to testify in person, but cancelled at the last minute when his wife went into labour.

Trump went on television to pre-emptively declare victory at the urging of Rudy Giuliani, a former New York City mayor. Campaign adviser Jason Miller testified that Giuliani was not sober at the time.

Monday’s session followed a blockbuster hearing on Thursday night featuring testimony showing that close Trump allies – even Trump’s daughter Ivanka – rejected his false claims of voting fraud. 

Nearly 20 million Americans watched the hearing aired in prime time.

Four people died the day of the attack. Some 140 police officers were injured, and one died the next day. Four officers later died by suicide.

Nearly 850 people have been arrested for crimes related to the riot.