I agree with you that a candidate with the majority of the vote cannot lose using the plurality method. A candidate with majority of the vote is considered to have more than fifty percent of the total votes, which also qualifies him or her to win with the plurality method (Smith, 2015). The plurality method simply considers the candidate who acquires more votes than others aspirants.
Smith, S. B. (2015). Chance, Strategy, and Choice: An Introduction to the Mathematics of Games and Elections. Cambridge University Press.