"Circus" was written by Dr. Luke, Benny Blanco and Claude Kelly, while produced by Luke and Blanco. Background vocals were provided by Cathy Dennis, Kelly and Myah Marie. Main instrumentation was done by Luke and Blanco. The song was mixed by Serban Ghenea at MixStar Studios in Virginia. "Circus" was announced on October 31, 2008, as the second single from the album, and was officially serviced to American radio stations on December 2, 2008.