Double Exposure

Columbo alludes to "Candidate for Crime" in both episodes that immediately followed it in the original broadcast schedule. In this episode, Columbo says he's been "working late on the Hayward case," referring to Nelson Hayward, the politician who murders his campaign manager in "Candidate for Crime," the preceding episode. This is an unusual acknowledgment that Columbo handles multiple cases at the same time. Then, in the next episode, "Publish or Perish," Columbo tells killer Riley Greenleaf (Jack Cassidy) that he wants to write a book about his experiences and describes, as an example, the plot of "Candidate for Crime," to which Greenleaf responds, "Lieutenant, very frankly, I don't give a damn about your Senator or your story."

When Columbo arrives at a back office with monitors, he's being tracked by a videocamera. He arrives and sees himself live on the monitor, filmed from behind. What he sees doesn't match with his actual position, judging by a hand resting against a wall.