Slattery, whose "Mad Men" co-star Jon Hamm is also a regular visitor to the popular sitcom, will play a candidate for Congress.
A three-time Emmy Award nominee for his work on "Mad Men," Slattery has been seen on Broadway in Rabbit Hole, Betrayal and Laughter on the 23rd Floor, and Off-Broadway in Three Days of Rain (Drama Desk nomination) and The Lisbon Traviata. Other television appearances include "Desperate Housewives," "Sex and the City" and "Will and Grace."