Final answer:
When a third-party candidate takes away decisive votes from one of the major party candidates, it is known as a spoiler.
Step-by-step explanation:
When someone of a 3rd party pulls decisive votes away from one of the major party candidates, it is known as a Spoiler. This happens when a candidate who is not expected to win takes away votes from a leading candidate, causing them to lose the election. For example, in the 2000 US presidential election, Ralph Nader ran as a third-party candidate and many believe he played the spoiler role by pulling votes away from Al Gore, potentially contributing to George W. Bush winning the election.
Learn more about Third-party candidates and their impact on major party candidates