I find it so funny how people want to discredit Christina by keep saying 'ACCELERATE WAS THE LEAD' when it never was confirmed to be the lead. Yes if you pick the dictionary 'lead' could mean 'first', but aslong as a single is not fully pushed and sent to radio, it is just simply a promotional release to promote the album and not the lead single. In this day and age a lead single doesn't have to be the first release.
Christina is not handling every release as a full length single, by that logic 'Twice' released apparently this week, would be the official 2nd single, while that song beside getting a visual will also just be an other promotional release.
Fall In Line is for now set to be the fully pushed single, I wouldn't be suprised if they are readying a radio deal, will push it on streaming, will have a higher budget for the video etc. etc. and by that it is the proper lead single.
It's funny since if Christina released Fall In Line last week, and Accelerate this week, people would probably call Accelerate 'promo' or 'buzz' single anyways.