During the action, a spectator is loudly cheering for Fencer X. What should the referee do?

When a spectator's cheering is loud enough to disrupt the focus and performance of the fencers, it creates an environment that could potentially affect the outcome of the bout. The referee's primary responsibility is to maintain a fair and controlled environment for both competitors. Therefore, if the cheering is indeed disruptive, the referee should call "Halt!" to pause the action, assess the situation, and determine if further action is necessary.

This approach ensures that the bout is conducted in a respectful and concentrated atmosphere, free from undue influence or distraction. It allows the referee to gauge whether the cheering is genuinely a problem and to address it accordingly, rather than prematurely taking more drastic measures such as asking spectators to leave or stopping the bout entirely without assessing the level of disruption first.