It was the first public appearance for the senator who admitted last week to having conducted an eight-month affair with a former campaign staffer who is married to one of his former top aides.

Several senators from both sides of the political aisle, including Democratic Sen. John Kerry of Massachusetts and Sen. Chuck schumer of New York, shook his hand. Republican Sen. Tom Coburn of Oklahoma, a housemate, stood by his side at the Nevadan's desk.

Citizens for Responsibility and Ethics in Washington expects to file the complaint with the Senate Ethics Committee by mid-week.