What happens to Sen. Bob Menendez's seat after his conviction?

New Jersey Democrat Bob Menendez has become one of very few U.S. senators convicted of a crime while in office. He's also the first to be convicted of being an agent of a foreign government. This raises questions about his ability to serve the rest of his term. The Constitution empowers Congress to expel a lawmaker with a two-thirds majority vote. Democrats have a tenuous hold on the majority. Whether they decide to pursue expulsion isn’t clear. Other senators throughout history who faced possible expulsion opted instead to resign. New Jersey law allows the governor to appoint a senator to fill a vacancy.