Who held the power in Athenian democracy?

The democracy in Athen included adult male citizens who chose to be part of it.

So who showed up?

Citizens who were rich enough to hold slave had free time to study philosophy and politics. All of the citizens in town when a legal case was argued were able to be part of a jury. However, a group of oligarchs was able to seize some power [ becoming more equal than the rest] and furthered there political ends by voting to banish troublesome citizens.

The powerful group changed but was alway small relative to the citizens.