Despite being out for a week and having no performances or video (not even an audio or lyric one on VEVO), Meghan Trainor's lead single NO hit #1 on iTunes. She dethroned Blake Shelton's song about Gwen and 7 Years and now has a nice lead. She is expected to possibly block Zayn's I Would and maybe even Ariana's Dangerous Woman out tonight.
A potential contributor for Meghan's 3-1 rise may be Selena Gomez's snapchat of her singing along to NO, since she has a big social media fan base.
Meghan also played a snippet from her album Thank You on snapchat
Source: Meghan's Official Instagram, Twitter 1, Twitter 2