Josh was shot and underwent major surgery to repair a pulmonary artery at the beginning of season 2. In this episode, we see him minus his shirt- and there's no evidence of a scar.
After returning to Josh's room, Donna says, "Tell me you found my pantyhose." However, In the first scene Donna's legs are bare.
When the Congressman and Helen return home from voting, he asked where the kids are. She replies "It's Tuesday. They're at school". This wouldn't be true in real life as all public schools are closed on election days as they're often times used as polling places.
In the Houston airport scene at 6:36AM, a number of American Airlines DC-10 or MD-11 aircraft are seen on the ramp. American Airlines would have retired all of those aircraft types by 2000, 6 years prior to the election. Additionally, they would not have a large presence at Houston which is primarily a Continental hub nor would they have such long range aircraft servicing it.
In the conversation between Bruno and Bob about the exit numbers, Bob mentions the state Of North Dakota has gone Republican for 40 years. In season 4 (Election Night) it is specifically mentioned, three times, that Bartlet won both of the Dakota states. In fact one of the people who says that Bartlet won the Dakotas in that episode, is Bruno Gianelli.