(verb, the act of bandwagoning) to become a supporter or fan of something, esp. a sports team, solely due to the said item or team's general success and/ or popularity. Bandwagoners are believed to compose a large portion of many pro sports franchises in the United States, including the New York Yankees and Los Angeles Lakers. In the sports world, bandwagoning is generally frowned upon as it is associated with selling out. Bandwagoning is often confused with "fair weathering," which is different because while bandwagoning involves switching teams, fair weathering is merely ceasing to follow a team when they are no longer successful.
Jim, a lifelong loyal Astros fan, was accused of bandwagoning by his brother Darren when he started rooting for the Yankees.