When discussing the Tea Party with Charlie Skinner, Will McAvoy says "Back in 1968, when Rennie Davis and Hayden and their guys organized the SDS, it was specifically to end the Vietnam War." Will is referring to Tom Hayden, ex-husband of Jane Fonda, who plays Leona Lansing.
Towards the beginning of the episode Elliot Hirsch says to Will about act of voting and electing a new Congress that they are 'looking at democracy at work and it is a beautiful thing'. This is an exact quote that C.J. Craig gives the press core during the second season of the west wing, 11 years earlier, the in regards to the Stackhouse filibuster happening in congress. The link being both shows and episodes written by Aaron Sorkin.
In the Newsroom panel at PaleyFest, Aaron Sorkin revealed that the character of Sloan Sabbith was meant to be a smaller character initially, but he made her more relevant to the story.
Jane Fonda (Leona Lansing) & Sam Waterston (Charlie Skinner) also worked together on Grace and Frankie (2015) as Grace Hanson & Sol Bergstein respectively.