The fundamental of something is the same as its purpose.
What is the fundamental, or purpose, of politics in human society? It is to maintain fairness in society. However, the purpose of politics in today's world is to achieve power. The reality is that laws and systems are created and enforced not to maintain fairness, but to achieve and maintain power.
Political activity refers to any activity aimed at achieving the purpose of maintaining fairness. However, today's political activity refers to all the activities that are necessary to acquire, exercise, and maintain power (nonsense, trickery, intimidation, hypocrisy, etc.).