After the second season, NBC considered canceling the show. What happened next was one of the most organized fan campaigns in the history of American television up to that point. Roddenberry and his office, recognizing that the show was in danger, mobilized the fan base they had been developing through science fiction conventions and fan publications. The campaign generated hundreds of thousands of letters to NBC — by some accounts over a million, though the precise figure is disputed — along with organized demonstrations and media coverage that cast the potential cancellation of *Star Trek* as a news event rather than a routine programming decision.
The campaign worked, to a degree: NBC renewed the show for a third season. The network’s response to the campaign, however, included a move that was interpreted by Roddenberry as a signal of NBC’s true assessment of the show’s commercial value. *Star Trek* was scheduled in the third season for Friday nights at 10 p.m. — a time slot then known in the industry as a “death slot,” a scheduling position that minimized a show’s audience by placing it in direct competition with the period of heaviest social activity for young viewers and in a time slot that research suggested attracted the smallest television audience of the week.
Roddenberry interpreted the Friday 10 p.m. scheduling as NBC’s way of technically renewing the show while practically ensuring it would fail. He stepped back from day-to-day production during the third season, delegating the producer role to Fred Freiberger. The third season is widely regarded as the weakest of the original series, though it contains individual episodes that the fan base has defended strongly.