His personal religious beliefs are of no political consequence.
However, since Islam has a political as well as a religious side, if he consistently votes for the Islamic position, then he is politically a Muslim.
Islam doesn’t have sides....Islam is a totalitarian fascist ideology counterfeiting a face of religion in order to keep their masses in check...has nothing to do with “religion” it’s all one mass of control and submission...and they intend to bring it to the world.