When Charlie and Mrs. Bartlet are speaking, she take off her earrings and then tosses them onto the bed, but when Charlies leaves and she sit down on the bed, her right ear clearly has an earring in it.
When Charlie interrupts Mrs. Bartlet reviewing the State of the Union on a recording, the last line heard from the speech talks about the "blue ribbon panel". When Charlie leaves and Abby resumes the recording, we hear President Bartlet repeat that same line again even though Abby had not rewound the recording.
The title of this episode indicates that this is President Bartlet's third State of the Union. However it would only be his second, as since 1989 American presidents have not considered the speech they give to a joint session of Congress early in their first year in office a State of the Union message, because they have not been in office for the previous year in order to reflect on it.
As a utility truck passes by the polling center (around 36 mins) you hear Donna say "You know what I'm surprised about" but her lips are not moving.