The truth is that we don't really know, because our sources for the first 3 decades of Perikles' dominance (461-431 BC) are very thin. We're pretty much just working with Thucydides' brief account of the pentekontaetia, the anonymous Constitution of the Athenians attributed to Aristotle, and later work like Plutarch's Life of Perikles. However, we can cobble together something like a general picture of Athenian politics and the development of the democracy in this period, and I've done so here.

If you have any follow-up questions to that post, feel free to ask!