Harrison Williams (D-NJ) resigned in 1982 as the Senate was about to take up a vote to expel him. From the same Senate seat that Menendez holds today. After being convicted on bribery and conspiracy charges.
It is worth noting there is a national security aspect to the Menendez situation. The charging documents indicate he provided information about the U.S. embassy staff to Egypt. Not classified information but still sensitive information that could have been used by the Egyptian government to undermine some of the work being carried out by the embassy staff.
NEW YORK — Sen. Bob Menendez (D-N.J.) was charged in a superseding federal indictment on Thursday with conspiracy by a public official to act as a foreign agent, intensifying the legal peril facing the veteran lawmaker as he continues to resist calls to resign.