Which leader is known as a junior founder of the CCP and served as its party chairman?

Mao Zedong is recognized as a junior founder of the Chinese Communist Party (CCP) and served as its party chairman. He played a pivotal role in the establishment of the CCP in 1921 and significantly influenced its direction and policies over the following decades. Mao's leadership style and revolutionary ideas shaped the party's ideology, leading to the Chinese Revolution and the establishment of the People's Republic of China in 1949. His tenure as party chairman lasted until his death in 1976, during which he implemented major political campaigns and cultural initiatives, such as the Great Leap Forward and the Cultural Revolution, fundamentally affecting Chinese society and governance.

In contrast, the other leaders mentioned in the options had significant roles in the CCP's history but did not co-found the party. Deng Xiaoping is known for his economic reforms in the late 20th century, Hu Jintao led during the early 21st century and emphasized a "Harmonious Society," while Jiang Zemin also contributed to the party's evolution but came into power later than Mao.