Senator Marco Rubio of Florida announced late Saturday that he had fired his chief of staff after allegations of improper conduct.

After an internal investigation, he determined that the employee had “violated office policies regarding proper relations between a supervisor and their subordinates,” Mr. Rubio said in a statement posted to his website. “I further concluded that this led to actions which in my judgment amounted to threats to withhold employment benefits.”

Mr. Rubio’s statement did not identify his chief of staff by name. Clint Reed is listed in that position in the Washington Information Directory published by Congressional Quarterly; he also identified himself as the chief of staff on his social media accounts as of early Sunday.

Mr. Reed did not reply to an email request for comment. He began working for Mr. Rubio when the senator was running for the Republican nomination for president in 2016, and ran Mr. Rubio’s campaign in Iowa. After Mr. Rubio ended his presidential bid, Mr. Reed ran his campaign for re-election to the Senate.