What tactic can senators use to prevent action on legislation they oppose?

The tactic that senators can use to prevent action on legislation they oppose is the filibuster. This parliamentary procedure allows a senator, or a group of senators, to prolong debate and delay or block a vote on a bill. By extending debate, they can create a situation where the majority may not be able to bring the legislation to a vote, effectively stalling the decision-making process.

The filibuster is an important tool in the Senate that allows for extended discussion on a topic, reflecting the body's unique role in the legislative process where minority opinions can be showcased and argued. Senators can speak for as long as they wish unless a cloture motion is invoked to end the debate, which requires a supermajority.

In contrast, the other tactics mentioned serve different functions: cloture is specifically a mechanism to terminate a filibuster, logrolling involves reciprocal trade-offs between legislators to secure votes for different pieces of legislation, and the whip system refers to the organizational structure that party leaders use to manage party discipline and voting alignment.