http://agathe.gr/democracy/ostracism.html
Ostracism In addition to the legal assassination condoned in the Law against Tyranny, a less extreme method was also available for removing powerful but dangerous men from public life. This was a formal, ... Ostraka cast against Aristeides, Themistokles, Kimon, and Perikles, fifth century B.C. ... It was his chief opponent, Aristeides son of Lysimachos of Alopeke (nicknamed “the just”), who received the greatest number of votes that year and so was ostracized.