The FBI's surprise decision to re-examine Hillary Clinton's use of a private email server before voters went to the polls cost her the election, the "heartbroken" Democratic nominee said Saturday, a source told NBC News.

The letter about the email inquiry — sent from FBI Director James Comey to Congress 11 days before the vote — raised doubts that helped to stop the campaign's momentum at a critical time, Clinton said in a farewell conference call with donors. A source who was on the call, which was reported by The Washington Post and others, confirmed Clinton's remarks to NBC News.



The source added that Clinton acknowledged that other factors contributed to her failed bid.



But Comey's closure of the inquiry just two days before the election on Tuesday boosted undecided voters in Donald Trump's favor even further, Clinton reportedly said.



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