| Alan Alda as | Arnold Vinick | Republican Candidate for President |
| Allison Janney as | C.J. (Claudia Jean) Cregg | Chief of Staff |
| Joshua Malina as | Will (William) Bailey | Communications Director |
| Janel Moloney as | Donna (Donnatella) Moss | Santos / McGarry Campaign Staffer |
| Richard Schiff as | Toby (Tobias Zachary) Ziegler | Former Communications Director |
| John Spencer as | Leo Thomas McGarry | Democratic Candidate for Vice President |
| Bradley Whitford as | Josh (Joshua) Lyman | Santos / McGarry Campaign Manager |
| with Jimmy Smits as |
Matthew Vincente Santos | Democratic Candidate for President |
| Special Guest Stars | ||
| Janeane Garofalo as | Louise "Lou" Thornton | Santos / McGarry Director of Communications |
| Ron Silver as | Bruno Gianelli | Vinick / Sullivan Campaign Strategist |
| Patricia Richardson as | Sheila Brooks | Vinick / Sullivan Campaign Manager |
| Guest Starring | ||
| Dean Norris as | Steve Hodder | Repubican Party Chairman |
| Lisa Darr as | Becca | Women's Alliance for Choice |
| NiCole Robinson as | Margaret Hooper | Assistant to Chief of Staff |
| Matthew Del Negro as | Bram (Howard) | Santos / McGarry Campaign Staffer |
| Ramón De Ocampo as | Otto | Santos / McGarry Campaign Staffer |
| Co-Starring | ||
| Alex Manette as | Reporter #1 | |
| Charles Noland as | Reporter #2 | Steve |
| Caroline Duncan as | Reporter #3 | Jane |
| Kerstin Lindquist as | Anchor |
[Janel] Moloney doubts Donna "will be an assistant anymore. She's kind of found her own voice. More than almost any other character on television, I think she's really grown up on the show."
"Moloney Moonlights as Frey"
by Jay Bobbin
May 22, 2005
zap2it.com
Spencer appeared in seven of the 14 episodes that have been filmed, nine of which have been broadcast.
"How series deal with death"
by William Keck
December 18, 2005
USA Today