Charlie Sykes, founder of The Bulwark website, said it was more important than ever that America observes Mr Trump as he prepares to leave office.
It comes as the defeated incumbent continues to falsely claim that the 2020 election was stolen from him while pushing unsubstantiated allegations of voter fraud.
Speaking on MSNBC‘s ‘Deadline: White House’ show, Mr Sykes cautioned that “there are no norms that he [Mr Trump] is not willing to violate, there’s no standard of decency that he is not willing to shred.”
He added: “We don’t know what the extent of the corruption is going to be. But what we do know is the president of the United States, right now in real-time, is trying to overturn a legitimate, democratic election.
“If somebody would have suggested a few years ago that we would be seeing a president of the United States that is actively trying to disenfranchise millions of voters to overturn an election and have himself declared the winner, people would have thought, oh, that’s Trump Derangement Syndrome. But that’s literally what’s going on right now.”
Meanwhile, Mr Trump late last month pardoned his first national security, general Michael Flynn, who twice admitted lying to the FBI about his contacts with Russia.
And there are fears that he is considering a raft of further pardons for his allies before finally leaving the Oval Office come January next year.
Earlier this week, unsealed court documents revealed the Department of Justice is probing an alleged “bribery for pardon” at the White House.
It came after reports suggested Mr Trump is a considering preemptive pardon for his children, son-in-law, and personal attorney, Rudy Giuliani.
The New York Times reported that two people briefed on the matter said Mr Trump fears a Biden Justice Department might seek reprisal against his three oldest children.
He has discussed pardons for Donald Trump Jr, Eric Trump, Ivanka and her husband Jared Kushner, as well as Mr Giuliani, the Times reported.
Mr Trump appeared to deny the claims on Tuesday night, branding them “Fake News!”