Sunday morning FiveThirtyEight’s star statistician Nate Silver tweeted that Hillary Clinton would likely have been elected to the White House if not for FBI Director James Comey’s October letter to Congress regarding the investigation into Clinton’s private email server.

“Comey had a large, measurable impact on the race. Harder to say with Russia/Wikileaks because it was drip-drip-drip,” Silver said in the first of a series of tweets about Comey’s possible influence in the election.

“I’ll put it like this: Clinton would almost certainly be President-elect if the election had been held on Oct. 27 (day before Comey letter),” Silver tweeted.

Comey in October sent a letter to lawmakers about the discovery of new emails it said were potentially relevant to the investigation into Clinton’s use of a private email server while serving as secretary of State. The emails were found during a separate FBI investigation into former Rep. Anthony Weiner. Weiner is the estranged husband of Huma Abedin.

Just days before the general election, Comey announced the FBI had not changed its July conclusion regarding Clinton’s private server. After the release of the first email in October, Republicans and members of Donald Trump’s campaign seized on the new information, attempting to cast Clinton as corrupt and praising the FBI for the development.

Since the election, Hillary Clinton and her aides have put blame on Comey for the Democratic nominee’s loss.

“There are lots of reasons why an election like this is not successful,” Clinton told donors on a conference call one week after the election. “Our analysis is that Comey’s letter raising doubts that were groundless, baseless, proven to be, stopped our momentum.”