why is a successful campaign called a "bandwagon"?

Question

What makes a band wagon gather speed better than any other wagon?

Answer 1

It's a term used for anything which a lot of people band together in.

However, the origins are suspected from P.T. Barnum's use of band-wagons, where he would have a band performing on a large, slow moving wagon, which people would then follow through town to the circus performance.

Answer 2

This website covers alot of the campaign videos and talks alot about the candidates if thats helpful for you as well.