The appearance for Representative Zach Nunn was another departure from previous norms for the defense secretary, whose predecessors kept a greater distance from politics.
Representative Jimmy Gomez of California acknowledged “personal mistakes” outside his marriage but denied breaking rules that bar relationships with a direct subordinate.
Mr. Gomez said that he regretted his mistakes, but he denied wrongdoing, saying that his actions “were consensual in nature and haven’t violated the law or House Ethics rules.”