SMM Platform

A platform in politics is a set of aims and principles upon which a party campaigns. Metaphorically, it is the set of ideas upon which someone stands, like a stage. Politicians stand on platforms, not hide under them.

Incorrect: Buhari, presidential candidate under the platform of the APC, ...

Correct: Buhari, presidential candidate on the platform of the APC, ...

 The correct phrase seems to have mated with 'under the umbrella of', meaning when a group or system provides protection or a 'home' to a collection of smaller groups or individuals:

Correct: The parties came together under the umbrella of the All Progressives Congress to fight the 2015 elections.