CNN  —  Prosecutors say former US Sen. Bob Menendez should be imprisoned for 15 years, after the Democrat from New Jersey became the first to be convicted of abusing a Senate committee leadership position and the first public official to be convicted of serving as a foreign agent. In papers filed late Thursday in Manhattan federal court , prosecutors called for the lengthy prison term for the 71-year-old Menendez when he is sentenced on January 29. Menendez was convicted in July of 16