A high-ranking union official who is also a Boston Redevelopment Authority board member pleaded not guilty Thursday after a judge refused to dismiss an allegation that the union official threatened an International Brotherhood of Electrical Workers colleague with a baseball bat.

Michael P. Monahan faces charges of assault with a dangerous weapon and making a threat to commit a crime during a Jan. 22 incident at a union office. Prosecutors allege that Monahan confronted Michael Baker, who he believed was spreading rumors about his pending divorce.

The two men have a long history of political disagreement, according to court documents filed by Monahan’s attorney, George C. McMahon, who said the rumors dated back 2½ years. Monahan claims Baker has previously accused him, in unsuccessful complaints to labor regulators, of making physical threats.

A conviction on the assault allegation would disqualify Monahan, an international vice president in the electrical workers’ regional office, from elected union posts, court documents say.

Baker, 44, of North Reading, went to police 16 days after the alleged attack, court documents say. He told investigators Monahan brandished the bat while making threats against the victim, his children, and two others. Monahan allegedly said he would act after his divorce became final.

“I will kill you, and you won’t even see it coming,’’ he is alleged to have said, according to court records.

McMahon said in Dorchester Municipal Court that Baker told private investigators he was working with the FBI when he made the allegations.

The probe has brought scrutiny to Mayor Martin J. Walsh’s administration and his work as a labor leader before taking office in 2014, according to people familiar with the inquiry.

McMahon also said the defense’s private investigators overheard Baker on the phone to a person identified as an FBI agent. In that conversation, according to McMahon, Baker said, “Don’t worry, I will not tell anybody that the FBI told me how to go after this complaint against Mr. Monahan.’’

McMahon said in an interview that Monahan plans to continue in his union and redevelopment authority roles. He was released Thursday on personal recognizance, according to the Suffolk district attorney’s office.

Andy Rosen can be reached at andrew.rosen@globe.com. Follow him on Twitter at @andyrosen.