Jean-Jacques Rousseau wrote [1]:



From where do politicians derive their power?

In a democracy, it is from the social contract made between citizens where they explicitly or implicitly decide to appoint some individuals to make laws, and other individuals to administer them.

The expectations are that citizens pay their taxes and that those in positions of authority act in a competent and fair way.

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References

[1]	The Social Contract (1762) Jean-Jacques Rousseau http://www.earlymoderntexts.com/assets/pdfs/rousseau1762.pdf