Former FBI agent Peter Strzok helped write the controversial letter to Congress sent by then-FBI Director James ComeyJames Brien Comey3 real problems Republicans need to address to win in 2020 Barr predicts progressive prosecutors will lead to 'more crime, more victims' James Comey shows our criminal justice system works as intended MORE announcing the reopening of the probe into Democratic presidential nominee Hillary ClintonHillary Diane Rodham ClintonTop Sanders adviser: Warren isn't competing for 'same pool of voters' Anti-Trump vets join Steyer group in pressing Democrats to impeach Trump Republicans plot comeback in New Jersey 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 TrumpTrump pushes back on recent polling data, says internal numbers are 'strongest we've had so far' Illinois state lawmaker apologizes for photos depicting mock assassination of Trump Scaramucci assembling team of former Cabinet members to speak out against Trump 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 MuellerTrump calls for probe of Obama book deal Democrats express private disappointment with Mueller testimony Kellyanne Conway: 'I'd like to know' if Mueller read his own report 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.