Crucial aspects of the Indian polity for UPSC Mains preparation include the Constitution, fundamental rights, governance structures, and the functioning of various institutions. Understanding the roles and powers of the President, Parliament, and Judiciary is vital. Aspirants should focus on policies, political parties, and electoral processes, along with current affairs related to governance. Additionally, exploring landmark Supreme Court judgments and recent amendments can enhance analytical skills, making these topics essential for scoring well in the Mains exam.