Sanders thinks that Trump is a pathological liar.
In a Friday interview with the The Guardian, Sanders claimed that Trump's "unprecedented" leadership was in fact a calculated maneuver to cement power.
Speaking to The Guardian, Mr Sanders, who challenged Hillary Clinton for the Democratic presidential nomination past year, said he believed Mr Trump's lies were an attempt on the President's part to "undermine the foundations of American democracy".
But to understand how the country got to a place of having a president Trump-as well as to strategize how to boot his CEO-profiting agenda-Sanders explains to the Guardian and in a new interview with the Huffington Post, is to understand the failures of the Democratic Party (the party with which he caucuses) over the last several decades. "He lies in order to undermine the foundations of American democracy".
He continued: "George Bush was a very conservative president, I opposed him every single day". The President's actions do not reflect who America is, do not respect the Constitution.
Sanders said Trump's open hostility to mainstream media, unsubstantiated claims of widespread voter fraud and delegitimization of the judiciary were part of a wider strategy to drive the United States towards authoritarianism.
Bernie Sanders would be the first person to tell you President Donald Trump's first few weeks in the Oval Office have been mired in controversies, to say the least.
The Senator thinks that Trump is slowly moving to authoritarianism.
But Sanders, a leader in the grassroots movement against Trump, said he was encouraged to see the large turnout of Americans at recent townhall meetings to speak out against Trump's proposed repeal of Obama's healthcare law.
"It is incumbent upon [Republicans], in this moment in history, to stand up and say that what Trump is doing is not what the United States is about", Mr Sanders said. "We've been quite successful in this, getting more and more people to run for office".
Liberal Sanders has been a vocal critic of the new White House chief - but his latest outburst made no bones about his feelings towards Trump. He recently described the revised version of Mr Trump's travel ban as "racist and anti-Islamic", and accused him of "stirring up fear and hatred against immigrants" after it emerged the President plans to regularly publish a list of crimes committed by non-US citizens.