Other forms: jumped on the bandwagon; jumping on the bandwagon; jumps on the bandwagon
To jump on the bandwagon means to do something just because other people are doing it. If all your friends start wearing black clothes, you may be tempted to jump on the bandwagon and ditch your colorful wardrobe.
People often jump on the bandwagon when they perceive a cause to be successful, like when someone supports a political candidate because it seems like they'll probably win the election. This idiom originated in 1848 when U.S. presidential candidate Zachary Taylor was invited to join a circus parade on a clown's bandwagon, an ornate wagon that carried performers and musicians. The phrase is somewhat derogatory, implying that those who jump on bandwagons are only interested in success or popularity.