I claimed cop in hopes of finding out who the mafia is. Zapfino, for reasons unknown, claimed cop very late, which is usually a sign of being with the mafia.

As I fully believed Zapfino was with the mafia, I saw no reason to retract my claim.

Schematic of my situation:

Not retracting:
+ Melieved mafia is lynched
+ Attention is drawn away from the real cop
+ I seem less likely to be with the mafia from the real cop's point of view
- The town might see me as a potential mafia

Retracting:
+ The real cop can lead
- The mafia knows exactly who the cop is
- Believed mafia might not be lynched