The phrase 'Jump on the Bandwagon' means to join in a popular activity.
Example of Use: "So many people are trying to quit smoking that I might as well jump on the bandwagon and quit as well."
The origin of the idiom 'jump on the bandwagon' is an interesting one. In nineteenth century America, a 'bandwagon' was a horse-drawn wagon with a platform for a group of musicians (a band) that often preceded a circus parade. The phrase was first seen in 1848, when a famous clown named Dan Rice would use his circus bandwagon to transport politicians around town while the music attracted the public to an area where campaign speeches were being given.