Still, Congress remains a workplace where victims say they have few effective avenues for recourse.

Mr. Meehan’s case sheds new light on secretive congressional processes for handling such complaints, which advocates say are slanted to favor abusers, allowing them to use the vast resources of the federal government to intimidate, isolate and silence their victims.

As a member of the Ethics Committee, Mr. Meehan was tasked with being a part of the solution. The panel has initiated investigations into sexual misconduct claims against at least four congressmen in recent months. Two have resigned: Trent Franks, Republican of Arizona, and John Conyers Jr., Democrat of Michigan. The other two, Blake Farenthold, Republican of Texas, and Ruben Kihuen, a freshman Democrat from Nevada, remain in office but have said they will not seek re-election.

Mr. Meehan has been pushing for protections for domestic violence victims since his time as a local prosecutor. In Congress, he has sponsored legislation mandating the reporting of sexual violence, and he is a member of a bipartisan congressional task force to end such violence.

This account is based on interviews with 10 people, including friends and former colleagues of the former aide and others who worked around the office. The New York Times is not naming the former aide, who followed the recommended procedures for reporting harassment but came away from the experience feeling traumatized, according to several people with whom she shared her feelings.

Mr. Meehan’s family was close to the former aide, according to friends and colleagues, and she was regarded as an integral employee in the office, according to people who worked in or around the office. They said Mr. Meehan seemed to favor her over other employees, so much so that others saw his favoritism as unprofessional. He expressed interest in her personal relationships outside the office, then seemed to become jealous in April when word spread through the office about the aide’s boyfriend. After Mr. Meehan’s professions of attraction and subsequent hostility, the woman filed a complaint with the congressional Office of Compliance over the summer, alleging sexual harassment.

The handling of that complaint — which included an aggressive pushback by representatives from Mr. Meehan’s office and congressional lawyers, who suggested she had misinterpreted the congressman’s behavior — demoralized the aide. It led to her estrangement from her colleagues, and isolation from friends, family and her boyfriend, according to the people in whom she confided. It set her back financially and professionally, as she continued to pay legal costs associated with the complaint even after leaving her job in Mr. Meehan’s office and struggling to find a new one. She moved back in with her parents and ultimately decided to start a new life abroad.