It is difficult to ascertain the ideological stance of the Nationalist Party of China because it has apparently changed over time and with the change of leadership. The Nationalist Party was founded by Sun Yat-sen in 1912 out of the revolutionary group he headed called, in Wade-Giles romanization, T'ung Meng Hui (Revolutionary Alliance). The original Revolutionary Alliance had been formed in 1905 in Tokyo among Chinese expatriates opposing the Imperial Ching Dynasty government. Sun was elected leader of the organization. By 1912 Sun saw the need for a formally organized political party.
Sun stated his political position in terms of Three Principles of the People, which were nationalism, democracy and economy. The economic element of his philosophy involved socialism. It was no wonder that socialism seemed a more attractive system to Sun coming as he did from a poor rural background and experiencing the problems of imperialistism impinging upon China. Sun background was more akin to a feudalist society than a market economy and, despite all the protests of the progressiveness of socialism by its advocates, socialism is fundamentally a utopian version of feudalism. This accounts for the undeniable fact that socialism most strongly appeals to people who are culturally not far away from feudal or tribalistic societies.
So it is not surprising that Sun's program was socialistic in its orientation and it is not surprising that in 1923-24 the Soviet Union would offer help to Sun's Guomindang Party. Sun neede help and no help was forthcoming from Britain, France, America or Japan. The price the Soviets demanded for their help was that Sun form an alliance with the newly organized Communist Party of China.
Under Sun's leadership the merging of the Communist Party members into the Nationalist Party went reasonably smoothly. Later luminaries of the Communist Party such as Mao Zedong and Zhou Enlai served in the Nationalist Party. The Communist Party of China still treats Sun Yat-sen as one of the founders of their movement. But Sun Yat-sen was suffering from cancer and died in 1925.
After a bit Chiang Kai Shek (Wade-Giles romanization) emerged as leader of the leftwing of Guomindang Party. The rightwing of the Guomindang was under the leadership of Hu Han-min. The communist members of the Guomindang were rising and they were perceived as a threat to Chiang. He did not take action until he had his army mobilized for the Northern Expedition. This Northern Expedition's purpose was to defeat the many war lords operating in central and norther China. This purpose was being acheived. When Chinag's army in 1927 came to Shanghai, where the Communist Party was very strong, Chiang decided to take care of the communist threat to his control of the Nationalist Party.
There were additional factors that provoked Chiang's actions. In March of 1926 Chiang had struck against Communists and Soviet adviser whom he believed were plotting against him. This incident was supposedly forgiven on both sides and the cooperataion of Nationalist and Communist elements continued. In the Norther Expedtion one branch of the Nationalist Army captured the city of Wuhan. The Guomindang government that emerged there was dominated by Communist Party members. In Shanghai there was an uprising that preceded the arrival of the Nationalist Army to the area. The uprising was put down by the local warlord but the uprising demonstrated the strength of communist influence in the labor unions. When the Nationalist troops entered Shanghai the labor unions under the leadership of Zhou Enlai established a town council that pre-empted the creation of a local government by the Guomindang. A final incident led to the fear that the communists within the Nationalist Army were pursuing their own agenda to the detriment of Chiang. This incident was an attack on the British, American and Japanese consulates by Nationalist troops when then entered Nanjing. Chiang believed the incident was communist inspired to provoke animoosity by foreign powers toward the Guomindang.
The Communists were machined gunned and the labor unions broken up. The extermination program was a success in the Shanghai area but the Communists in the south escaped the pograom and formed a governemt in the rural interior of South China. Mao Zedong was the primary leader of this movement.