Toby: What if I do it? I'll do all the negotiating, you'll have total deniability, no one else in this building has to know.
Bartlet: And if it blows up, I'm supposed to pretend we've never met?
Toby: We'll always have Paris.
"We'll always have Paris" is one of the most famous lines in the history of the film industry (it was voted 43rd in AFI's "100 Years... 100 Movie Quotes"). It's a line from the 1942 film Casablanca, where Rick tells "we'll always..." to Ilsa, meaning they'll have the memory of the peak of their love.