Final answer:
A senator can prevent a vote in the Senate by filibustering, which extends debate to delay or block legislation, requiring a supermajority of 60 votes for a cloture motion to end the filibuster.
Step-by-step explanation:
A senator can effectively prevent the Senate from voting by filibustering. A filibuster is a parliamentary procedure where debate over a proposed piece of legislation is extended, allowing one or more members to delay or entirely prevent a vote on the proposal. This tactic exploits the tradition of unlimited debate in the U.S Senate and relies on a de facto supermajority requirement for legislation to pass, as a vote only happens when 60 senators vote in favor of a cloture motion to end the debate. If a senator declares they are filibustering, the issue cannot come to a vote until the filibuster is resolved, which gives the ability to a single senator or a minority group to exercise considerable power to block legislation.