When the comptrollers wife pours the drink in Dee's face, the scene right after shows the drink still full on the table.
When Mac is asked to get in the car the right rear window is closed, yet the first thing he does upon getting in the car is to close that window.
(at around 8 mins) As Mac is leaving the union office a camera man wearing a black shirt can be seen to the left of the screen.
From around 7 to 8 mins when Mac is at the Union Office, wires can be seen a couple of times (non consecutive shots) on the middle right side.
When Charlie is preparing to film Dennis in front of the million-dollar towel, a camera can briefly be seen over his left shoulder on the far right side of the screen.
At around 5 minutes, during an attempt to get Dennis to fire Frank and hire Charlie as the campaign manager, Charlie accidentally refers to Dennis as Glenn.