I am updating this article the day after election day 2020 in the US. It is still applicable, perhaps more so. With the rise of populism and the catering to special interests, we are witnessing the decay of a republic into an eventual oligarchy (if we last that long).
Original article:
Here is a thought-provoking video. It indirectly points out how Rome declined when corrupt politicians began to create welfare programs that eventually led to feelings of entitlement among the citizens. It also shows the dangers of small groups of people accumulating too much power. Rome started out as a republic, but it was eventually led by the Caesars.