How to Set Term Limits Without Setting Term Limits
It's really quite simple, every time you run for re-election, you have to win by a greater margin than you did in the previous election. So, the first time you're elected, if "x" is the number of votes cast, you have to win 0.5x + 1 in order to win. If you stand for reelection, you have to win 0.51x + 1 votes to win, a second reelection would require 0.52x + 1 to win, and so on. This would automatically offset the incumbent's advantage in seeking re-election, but it would allow a truly popular and effective leader to win more terms than a strict term limit allows.