Final answer:
Cleisthenes was instrumental in the establishment of Athenian democracy by overthrowing the pro-Spartan regime and implementing radical reforms that allowed all male citizens to vote and be eligible for public office, creating the first 'real' democracy in history.
Step-by-step explanation:
During the late 6th century BCE, Cleisthenes emerged as an influential figure in Athenian politics. In the power vacuum following the rule of the tyrant Pisistratus and his less popular successors, Cleisthenes successfully appealed to the common people, the demēs, of Athens. His aim was to overthrow the pro-Spartan regime that was established by the Spartans, who supported the Athenian aristocracy rather than the broader population. To accomplish this and to fend off a potential civil war, Cleisthenes introduced radical democratic reforms which included establishing a new council of five hundred members, drawing from all Athenian citizens, and reorganizing the Athenian populace into ten tribes that encompassed diverse regions, promoting a unified Athenian identity over familial or regional loyalties.
Under Cleisthenes, lawmakers were chosen by lot, ensuring that even those citizens who were too poor to afford weapons and serve as hoplites had a say in the government. This made Athens the first 'real' democracy in history, as all free male citizens could vote and hold public office. His reforms, which followed the earlier efforts of Solon to curb aristocratic power, set the foundations for future leaders like Pericles to continue promoting democratic institutions and engaging the citizenry in self-governance.