Former FBI agent Peter Strzok helped write the controversial letter to Congress sent by then-FBI Director James ComeyJames Brien ComeyNYT: Justice investigating alleged Comey leak of years-old classified info Bernie-Hillary echoes seen in Biden-Sanders primary fight Rosenstein on his time in Trump administration: 'We got all the big issues right' MORE announcing the reopening of the probe into Democratic presidential nominee Hillary ClintonHillary Diane Rodham ClintonFormer Vermont Governor: Sanders 'will play dirty' NYT: Justice investigating alleged Comey leak of years-old classified info New Hampshire state lawmaker switches support from Warren to Klobuchar MORE, according to emails obtained by CNN. 

Strzok, who in 2016 sent dozens of anti-Trump text messages in what conservatives have called clear evidence of bias, co-wrote the first draft of the letter but was unsure about reopening the investigation so close to the election, sources told CNN in a report published Wednesday. 

The day after Strzok sent his draft to colleagues, Comey released the final version of the letter, bringing Clinton's emails back into the spotlight just weeks before Election Day.

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Comey reopened the investigation that October, when thousands of emails of Clinton's surfaced on the laptop of former aide Huma Abedin's husband Anthony Weiner in a separate investigation. 

Clinton and top Democrats have said the letter was a key factor in her election loss to President TrumpDonald John TrumpLev Parnas implicates Rick Perry, says Giuliani had him pressure Ukraine to announce Biden probe Saudi Arabia paid 0 million for cost of US troops in area Parnas claims ex-Trump attorney visited him in jail, asked him to sacrifice himself for president MORE.

Comey has said that it made him "mildly nauseous" to think that reopening the Clinton probe may have swayed the election, but that he would have made the same decision again.

Strzok later went on to work on the Justice Department's probe into possible collusion between the Trump campaign and Russia, but was removed by special counsel Robert MuellerRobert (Bob) Swan MuellerSchiff: Trump acquittal in Senate trial would not signal a 'failure' Jeffries blasts Trump for attack on Thunberg at impeachment hearing Live coverage: House Judiciary to vote on impeachment after surprise delay MORE after the politically charged texts he exchanged with an FBI lawyer were revealed.

Trump and congressional Republicans say the texts are evidence that the probe into the Trump campaign is biased, while Democrats say they are trying to undercut Mueller's credibility. 

Trump accused Strzok of "treason" in a Wall Street Journal interview earlier this month.

Strzok also reportedly edited a key line in Comey's statement in July 2016 originally announcing Clinton would face no charges over her "home brew" server. He changed the phrase "grossly negligent" to "extremely careless" in regards to her actions.