AHMEDABAD, India — The resentment built slowly in Hardik Patel. It took root when he watched his younger sister lose out on a college scholarship because of India’s version of affirmative action, a system of strict quotas that reserves nearly half of government jobs and public college slots for those who come from disadvantaged castes or tribes.

It deepened as he talked to other young Patels from his farming village, where it seemed as if everyone had a story of a job lost, a door closed, or a dream thwarted all because the Patel clan is considered too well off to qualify for inclusion in India’s quota system.

This spring, with help from a loose network of friends, Hardik Patel began organizing Patels all over Gujarat, a western state of 63 million people, including roughly 10 million Patels. Meeting at farmhouses and restaurants, connecting on Facebook and WhatsApp, they quickly turned their shared resentment into an audacious plan that culminated on Tuesday when Hardik Patel, a baby-faced 22-year-old, stood on a stage here before 500,000 wildly cheering people, almost all of them young Patel men, and took dead aim at an entrenched quota system that India’s leading politicians have spent decades defending and expanding as a means to win votes from one caste or another.

In an act of political jujitsu, Mr. Patel demanded that the Patels, who belong to the Patidar caste, be included in the very quota system they despise — knowing that if the wealthy and politically powerful Patels of Gujarat can qualify for special quotas, then so must every other caste in India.