Clinton made the remark on a roughly 30-minute conference call with Democrats who raised more than $100,000, according to Politico.
The former State Department leader lost in a surprising defeat to Republican nominee Donald Trump -- a first-time candidate who essentially trailed in almost every major poll for the entire campaign.
FBI Director James Comey told Congress in an Oct. 30 letter that the agency was looking at emails found in an unrelated case that could be related to a closed FBI case specifically about the Clinton emails.
Clinton suggested her campaign’s internal poll numbers plunged after the letter but nevertheless rebounded, a person on the Saturday call told Politico.
However, she said the second Comey letter, three days before Election Day, saying that she had essentially been cleared in the unrelated case, awakened Trump voters.    
The FBI investigated Clinton using a private email server system while secretary of state. Comey said some of the emails included classified information and that she was “extremely careless” in her action. But he concluded the case in July without recommending criminal charges.
Clinton on Thursday told her campaign staff that she had “stepped in it” by saying half of Trump’s supporters were “deplorables,” according to The New York Times.
She and her campaign essentially defended the remark by saying she regretted saying “half” of the supporters were “racist, sexist, homophobic, xenophobic, Islamophobic" people.
Fox News' Serafin Gomez contributed to this report.