The Nevada Republican, who has been embattled since revealing he had an affair with the wife of a former aide, was facing a possible primary challenge from Rep. Dean Heller (R). Heller is now expected to run for the open Senate seat.
Ensign was facing growing pressure to exit the Senate race, and he has mounting legal bills related to his admission of the extramarital affair. He is the eighth Senator and third Republican to announce retirement this Congress. To see who else is leaving, check out our Casualty List.
Roll Call Politics currently rates the Nevada Senate race as a Tossup.
Vice President Joe Biden waits to conduct a mock swearing-in ceremony with Sen. Brian Schatz, D-Hawaii, in the Capitol's Old Senate Chamber, December 2, 2014. Schatz was sworn in to serve the remainder of his term since he was appointed to the seat after Sen. Daniel Inouye, D-Hawaii, passed away.