The "spoiler effect" occurs in elections when a third-party candidate draws votes away from a major candidate, potentially altering the outcome. This can lead to a situation where the candidate who is least preferred by the majority wins, as the votes are split among similar candidates. For example, in the 2000 U.S. presidential election, the presence of Ralph Nader, a Green Party candidate, is often cited as a factor that contributed to George W. Bush winning over Al Gore. Many believe that Nader's supporters would have otherwise voted for Gore, demonstrating how a third-party candidate can unintentionally influence the election results.