bubble under

verb3

1. •
   To remain beneath a level.

   • The results bubbled under the limit.
2. •
   To be in the background or margins of a phenomenon.

   • The Republicans were bubbling under in the area, waiting for an electoral break.
3. •
   To be successful on a modest scale, without yet being fully established.

   • The band was still bubbling under then, but their fame was about to explode.