Although the action of the film covers only a few days, Kevin Calhoun's (John Cusack) weight appears to fluctuate considerably from scene to scene.
A same extra (man with dark glasses) can be seen walking twice on the shot with Kevin Calhoun making his campaign at the ending. First, Kevin gives a leaflet to the man, who accepts it and takes the subway route. A few frames later, the same guy appears but this time he refuses the leaflet and goes to the subway (again).
When Kevin Calhoun and Marybeth Cogan are out on the boat, shots from the inside seem to indicate that the water is choppy, but exterior shots show calm water.
During the final discussion between the mayor and his deputy the mayor's vest is suddenly unbuttoned.
Coffins at NYPD funerals are covered with the NYPD flag which has 5 alternating green and white stripes and a field of blue with 24 stars in a circular pattern in the left, upper corner. They are not covered with US flags as in this film.
When Kevin goes to use the pay phone in the diner after Marybeth leaves, he dials successfully without putting any change in the phone first.
As Frank Anselmo is entering his house you can see a crewmember walking in front of his window in the bottom left hand corner.
When Kevin and Marybeth are returning from Buffalo, they get off of a NJ Transit train.
A newscaster refers to the shooting as having taken place on Broadway and Marcy Street. The location should have been referred to as Marcy Avenue. Several times other characters do refer to the location properly.
When Kevin signs to the Mayor to cut his speech short and he cuts it to present Tokyo's governor with an award, the governor stands up to greet the mayor before being completely announced. That means that the Japanese actor rushed his entrance.