Harry Reid

"I am writing to inform you that my office has determined that these actions may violate the Hatch Act, which bars FBI officials from using their official authority to influence an election," Reid wrote. "Through your partisan actions, you may have broken the law."

Reid, who is retiring from the Senate at the end of his term, added that Comey's "highly selective approach to publicizing information, along with your timing, was intended for the success or failure of a partisan candidate or political group."