As the keywords indicate, the two answers to this flat differ by a single letter. The first answer has one more letter than the second, without any other re-arrangement of letters.

I've served as leader long enough.

It's time for me to STING.

The change will do us all some good. 

Let someone else now SING.

Answer:

 

RESIGN - REIGN

 

Credit:

The Enigma

July, 2020

A. Chemem