One who climbs or gets on or aboard the bandwagon, in the United States, is he who accepts or espouses a popular movement or cause that some leader has organized.
It had a political origin, from the parades honoring a candidate for office and led by a loud band of musicians riding upon a large dray.
For the effect upon his constituents, some local leader would, as the band approached, vauntingly mount the wagon and ride through his district, thus advertising his endorsement of the candidate.
Though the band, the wagon, and the practice were long a feature in American pre-election politics, the phrase dates only from the second presidential campaign of William Jennings Bryan.
