What was a major cause of the
decline of empires in ancient times?

Invasions by Barbarian tribes. The most straightforward theory for Western Rome's collapse pins the fall on a string of military losses sustained against outside forces. Rome had tangled with Germanic tribes for centuries, but by the 300s “barbarian” groups like the Goths had encroached beyond the Empire's borders.

Candidate-centered elections

Explanation:

Candidate-centered elections refers to a political system where individual candidates decide to run, raise their

own money, and design their own strategy.

In this scenario, an individual candidate can fund his political ambition and run for a political post without a political party.