Factual error: Early in the episode, when Abby complains about who in their right mind would schedule outdoor inaugurations in January, Jed retorts by listing Jefferson, Adams, and Franklin, but inaugurations were in March until 1936 - not a mistake President Bartlet would make.
Factual error: When the president signs Toby's Presidential Pardon you can see his name listed as "Toby." However such a document would refer to someone by their full, legal name. In this case the document should say "Tobias" not Toby, which, although commonly used throughout the series, is still only a nickname.
Factual error: In the show's final scene Ronna comes into the oval office to remind President Santos that it's nearly 6 PM and he needs to get ready for the various inaugural balls. The Oval Office is filled with sunshine, however in Washington D.C. in January the sun would have set nearly an hour before and it would be dark outside.
Chosen answer: A really annoying innate lack of sense. My friends and family say the same thing all the time, and I'm endlessly trying to correct them. I think people just don't know any better and (ironically) couldn't care less that they're speaking incorrectly.