Why was the Alcmaeonid family’s religious curse used against Pericles?

The Alcmaeonid family’s religious curse originated from an incident during the 7th century BCE, when members of the family were accused of sacrilege and murder after followers of the failed tyrant Cylon were killed at an altar sanctuary. This act incurred a "bloodguilt" that persisted for centuries, serving as a recurring tool in Athenian political struggles.1

Because Pericles was descended from the Alcmaeonids through his mother, Agariste, his political opponents occasionally invoked this hereditary religious defilement to discredit him. By framing Pericles as tainted by his family's ancient sacrilege, his enemies sought to undermine his authority and influence. Notably, at the onset of the Peloponnesian War, Sparta demanded the expulsion of the Alcmaeonids as a calculated provocation specifically intended to target and weaken Pericles’ leadership.21