Hillary ClintonHillary Diane Rodham ClintonBernie Sanders: Trump 'so tough' on child separations but not on Putin Anti-Trump protests outside White House continue into fifth night Opera singers perform outside White House during fourth day of protests MORE in an interview Wednesday to promote her new book again blamed FBI Director James Comey for her “distressing” defeat in last year's presidential election.

"The role that he played historically was determinative," Clinton said of Comey in an interview on "Today" on NBC.

Clinton has previously slammed Comey for his decision to send a letter to Congress just more than a week before the Election Day to say he was renewing the investigation into whether Clinton sent classified information knowingly over a private email server while secretary of State.

The email controversy dogged Clinton's campaign throughout the election season, but Comey's announcement was a huge October surprise coming so close to Election Day.

"I thought, what is he doing? The investigation is closed. I knew there was no new information. And then it became clear. This was not necessary,” Clinton said about the letter.

“I was just dumbfounded," the former Democratic candidate said, claiming Comey "went way beyond his role" and largely influenced the outcome of the election.

“It stopped my momentum, it drove voters from me — understandably … so I think that in terms of my personal defeat was the most important factor,” Clinton said. 

“Absent that, I believe, and I think the evidence shows, I would have won.”

Clinton is on a promotional tour to highlight her new book, "What Happened," an account of her loss to President Trump.

While Clinton couldn't say whether she lost because of Russia's meddling in the election, or any actions that might have taken place between Trump's campaign and Russia, she said there had been a "lot of interesting coincidences" in terms of actions by Russia and the Trump team.