WASHINGTON — Representative Ruben Kihuen, a freshman Democrat from Nevada who has been accused of sexual harassment, said Saturday that he would not seek re-election. He is the fifth member of Congress in the past two weeks whose career has been derailed as part of the national reckoning over sexual misconduct.

In a statement issued by his office, Mr. Kihuen, 37, said he wanted to “state clearly” that he denied the allegations against him. He said that he would cooperate with the House Ethics Committee, which disclosed on Friday that it had opened an investigation into him, and that he looked “forward to clearing my name.”

But he said he was concerned that the allegations would be “a distraction from a fair and thorough discussion of the issues in a re-election campaign.”

Representative Nancy Pelosi, the House Democratic leader, had repeatedly called for Mr. Kihuen to resign. But until Saturday, he had steadfastly resisted doing so, insisting he had done nothing wrong.