Cody Simpson, Witney Carson Cody Simpson, Witney Carson

Dancing with the Stars drew Monday's biggest audience, but tied its lowest-rated premiere ever.

The Season 18 opener averaged 15 million viewers and a 2.5 in the adults 18-to-49 demographic, down seven tenths from last spring's premiere and six tenths from the fall premiere to match the all-time low posted by Season 15's All-Stars debut. Neither last spring's nor the fall's premieres went up against The Voice. Castle (9.9 million, 1.8) followed, up two tenths from its last new episode.

NBC topped the night with The Voice (13.3 million, 4.0), which grew 8 percent, and The Blacklist  (11.1 million, 2.8), which inched up a tenth.

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