bandwagon

A large wagon used to carry a band of musicians in a parade.

A current movement that attracts wide support.figuratively

• Specifically, and unforgivably, she restarted the Heathrow Third Runway bandwagon, which had been stalled for more than a decade and even declared dead by most commentators.

To join a bandwagon (a current movement that attracts wide support).figuratively

• Again, only three years ago, he opposed every measure advocated by Woodrow Wilson—did all he could to prevent his nomination—and bandwagoned when the nomination could no longer be prevented.
• “Weeping Walter” is a notorious example of the theory that “trimming” pays in politix. He has blown with every wind; he has bandwagoned with every passing movement from the Ku Klux Klan to the Townsend plan; […]