Which term would you use to describe a legislative tactic that involves lengthy speeches to prevent a vote?

The term that accurately describes a legislative tactic involving lengthy speeches to delay or prevent a vote is "filibuster." This parliamentary procedure is often employed in legislative bodies, particularly in the United States Senate, where members can extend debate on a piece of legislation, thus obstructing its passage. By talking for an extended period, the individual or group aims to either draw attention to a particular issue or force a compromise, effectively stalling the voting process.

In contrast, a "fallacy" refers to a flaw in reasoning or argumentation, which has no connection to legislative tactics. The term "forsake" means to abandon or renounce something and does not pertain to legislative procedures. Finally, "fervor" relates to intense and passionate feelings, which, while it may describe the emotions surrounding a debate, does not denote any specific tactics used in legislative contexts. Therefore, "filibuster" is the most appropriate term in this context.