Voting “no” in a room full of yes votes takes more backbone than anything else on the agenda.

A recorded vote is harder than a spoken doubt, because it goes on the list with your name next to it and cannot be softened afterwards. Unanimity is comfortable and often false, and the pressure to complete it is enormous. What you are protecting when you break it is your ability to mean your yes.

Decide before the room how you would vote if nobody else were present, and then vote that way. Give your reason in one sentence and do not campaign. Being outvoted while honest is a good outcome; being counted in a number you did not believe is not.