The former US secretary of state told Sway, a New York Times Opinion podcast, that she “can’t entertain the idea of [Trump] winning” the 2020 election, which takes place in a week's time.
"It makes me literally sick to my stomach to think that we'd have four more years of this abuse and destruction of our institutions,” she told the podcast, as The Hill reported.
“And [the] damaging of our norms and our values. And lessening of our leadership. And the list goes on,” she continued. “It would cause cognitive dissonance of a grave degree."
The 2016 Democratic presidential nominee went on to berate Republicans who had enabled Trump’s administration, saying they were “spineless” and “cowards”.
Still, "most Republicans are going to want to close the page," said Ms Clinton. "They want to see him gone as much as we do, but they can't say it publicly."
She went on to say that there was “no doubt” she would have handled the current health crisis better than president Trump, who has continued to say the United States was “rounding the turn” on the pandemic.
"I have no doubt, especially if it were me. I have no doubt. I mean, I was born for that,” Ms Clinton told Sway, in the episode available on Monday.
Those comments came as the United States recorded new single-day highs for coronavirus infections on two consecutive days, with more than 84,000 new cases on Saturday.
More than 8 million Americans have now been infected with coronavirus, and over 220,000 killed.
Mr Trump, adding on Sunday that his administration had done “maybe a great job” handling the health crisis, trails his 2020 Democratic opponent, Joe Biden, by an average of 10 points in national opinion polls.