As expected, Sen. Robert Menendez (D-NJ) has been indicted by the Department of Justice (DOJ) on a number of corruption charges stemming from his relationship with a Miami donor. Menendez has consistently denied the allegations and prior to and after being re-elected in 2012, claimed the DOJ's investigation was a political smear job. Then, and now, the head of the DOJ, the executive branch of the federal government, and Menendez were all members of the same party.
If Mendendez resigns, a replacement would be chosen by Gov. Chris Christie, a Republican, with a special election likely to follow later in the year. Given Menendez' consistent denial of wrongdoing, it's far from certain that he will resign. Only 15 senators have been expelled from the legislative body in its over 200 year history, 14 for supporting the Confederacy during the Civil War, and another in 1797 for treason and an anti-Spanish conspiracy. According to the Senate Historical Office, only four senators have ever been convicted of crimes while in office.
See previous coverage of the evolving Menendez scandal here.