Clinton's call with her top donors was not open to the press, but a source told ABC News that the tone was somber, with Clinton thanking those on the call and referring to the election results as a "very tough loss."
Similar to what her campaign chair, John Podesta, said on a call with donors and supporters Friday, Clinton placed most of the blame for the loss on the letter Comey sent to congressional leaders on Oct. 28, 11 days before the election, announcing a review of newly-discovered emails that were potentially related to the investigation into Clinton's use of a private email server as secretary of state.
Clinton said her campaign had felt confident in their chances of victory after the third and final presidential debate in Las Vegas on Oct. 20.
But she said the FBI director's letter eight days later did two things: It killed momentum in her campaign and boosted motivation for Trump.
Comey issued a second announcement on Nov. 6, two days before the election, that the review had reaffirmed an earlier conclusion by the FBI that no criminal charges were warranted over the emails.
Clinton also told donors today that she is "concerned" and "deeply saddened" for Americans who she said are now living in fear following the election of Trump. She called on the group to stand up for the people who may not be able to defend themselves.
The source said Clinton did not address her future plans.
Clinton's comments to her top donors were similar to remarks that top staffers in her campaign made on a call with donors and supporters Friday, sources told ABC News.
Donors on the call were told that the campaign was going well until the Comey letter surfaced on Oct. 28, sources told ABC News. The campaign noticed a change in the attitude of voters and that change was accelerated by the second letter from Comey on Nov. 6 saying that no charges were called for, top staffers told donors on the Friday call.
The campaign found that the Nov. 6 letter helped Trump by bolstering his narrative that the system is rigged.
A top donor told ABC News that the Comey letter was "a perfect setup for failure" and added that the "donor community is 100 percent behind Hillary Clinton and the campaign."
"It's a very sad outcome," the donor said.