Fandom: The West Wing
Pairing: Donna Moss/Josh Lymen
Title: A Winning Strategy
Author: jo_march and Ryo Sen
Why This Must Be Read: This series is one of the classics of the fandom and it has it all: AU (after season one), the ever popular “Secretly Married” trope, and amazing writing.
There are something like 30 stories in this series. You're welcome.