In 510 B.C., Cleisthenes wanted to bring his family, the Alcmaeonids, into power. The opportunity came when the last tyrant, Hippias, was exiled and the position of leader of Attica (the area around Athens) was left open. Cleisthenes gathered the common people and received their backing by promising them changes in their favor, including the right to vote in the Assembly. They helped to put him in power and soon afterwards he began his changes.

Cleisthenes started by making a fundamental change in the electoral system of Attica . He redivided the Athenian citizenry into ten new electoral districts, called tribes. Each tribe had precincts from the city proper, the coastal district, and the inland areas. Each precinct chose men who were over 30 years of age for the Council of 500, or Boule. The Council of 500 consisted of 50 representatives, who were chosen by lot (that means by a lottery) out of all the candidates from each tribe. Thus the 500 representatives were selected from the men who had been elected so as to deter any group influence.

After much scrutiny the 500 were accepted. After being accepted they would take an oath to do what was best for the state, and they began their terms at the beginning of the year.

The council was divided into 10 subcommittees (50 from each tribe) and in turn each subcommittee would be in charge of the general government decisions for about one tenth of the year. After their turn was up the next subcommittee would take over.

Term limits: Each member of the council of 500 could only serve for one year. No one could serve two years in a row. Also no one could serve more than twice.

Cleisthenes set up 170 demes, small areas, where a citizen was registered as a citizen and a voter. This helped to put everyone on an equal footing. There was nothing in the register that showed whether a citizen was of ancient descent or if he or she had recently arrived in Greece. This allowed foreigners and ex-slaves to also become citizens, who had never been given the opportunity before. He got a lot of political support from helping these people