"Idol" runner-up Bo Bice took the second spot with "Inside Your Heaven." Underwood was in first place last week with her version of the same song.
Carey's hit, from her album "The Emancipation of Mimi," has headed the list for five weeks.
The same three names pop up elsewhere on the charts. Bice has the top-selling single with "Inside Your Heaven" and his cover of "Vehicle" by the Ides of March. Underwood's "Heaven" dropped from No. 1 to No. 2.
"Together" leads the Hot R&B/Hip-Hop list for the sixth consecutive week.
The Black Eyed Peas' "Don't Phunk With My Heart" heads the Hot Digital Songs list for a third week, while "Just a Lil Bit" by 50 Cent is at the top of the Hot Ringtones list.