candidate (n.)

"person who seeks or is put forward for an office by election or appointment," c. 1600, from Latin candidatus "one aspiring to office," originally "white-robed," past participle of candidare "to make white or bright," from candidus, past participle of candere "to shine" (from PIE root *kand- "to shine").

White was the usual color of the Roman toga, but office-seekers in ancient Rome wore a gleaming white toga (toga candida), probably whitened with fine powdered chalk, presumably to indicate the purity of their intentions in seeking a role in civic affairs.