The West Wing
's Donna ain't lovelorn no more.
is joining the cast of Showtime's
for at least four episodes this season, playing a woman who has an affair with Jason Clarke's ambitious politico. (All together now:
Poor Annabeth Gish
In other Showtime news, in addition to
for at least 10 episodes (first scooped by the
, he'll serve as a love interest for both Nancy and Celia),
's krazy Kat is returning for the Season 3 opener, while
will guest this season as Celia's "May-the-divorce-be-with-you" lawyer.