Kamal was hardly 26 and totally subsumed by his interest in the humanities when he was cast into the leadership of his Druze community after the death of his uncle Hikmat Jumblatt in 1943. He was caught unprepared and became a politician "by chance." Between then and 1977 he led an active political life in his own right, serving continuously as a member of parliament and leader of a parliamentary bloc, with a short interruption between 1957 and 1960. He was appointed cabinet minister seven times between 1946 and 1970. Jumblatt was in the opposition even when he, or those he deputized, were in government. Whenever he took office he did so with the intention of utilizing the uniquely Lebanese institution of built-in opposition to discreetly promote his political programs and reinforce his influence. His clout in presidential elections earned him the label "king-maker."

Despite overwhelming indications—ranging from his education to his mother's political closeness to French authorities —that Jumblatt was groomed to be yet another pro-French politician, soon after his election in 1943 he backed the struggle for independence from France. He gradually became a leading advocate of socialism, decolonization, and non-alignment. Jumblatt derived influence from nurturing an ever-growing number of political groups clamoring for reform. In 1949 he launched the Progressive Socialist party (PSP), which gradually shrunk from an indigenous socialist-humanist movement into a predominantly Druze political association. In 1951 he was instrumental in establishing the Socialist National Front, which played a central role in forcing the resignation of President Bishara al-Khoury in 1952. When the front succeeded in putting one of its members, Camile Chamoun, in the presidency, the reform plank Chamoun was willing to adopt did not quench Jumblatt's thirst; the front dissipated.

This experience was a turning point in Kamal Jumblatt's political life. Frustrated with the gradualist approach of his allies, he set out on a course to destroy the consociational system of government engineered by the National Pact of 1943 after having earlier described it as a "free" and "tolerant" system of "consultation and democracy" and "a great attempt to coordinate and harmonize the relationship between Christianity and Islam." By 1958 Jumblatt was not only willing to participate in a war against the regime, but was one of the engineers of that war.

Beginning in the mid-1960s his allies were openly the radicals, including the Communists, Nasserites, and Arab nationalist groups. The new alliance, labeled the Front of Progressive parties and National Forces, evolved into the National Movement after the mid-1970s. In the same vein, Jumblatt championed the Palestine cause for a national homeland and went into open alliance with the Palestine Liberation Organization (PLO) against the government after 1967. As minister of interior in 1970 he licensed the Communist party of Lebanon and the Syrian Nationalist Social party, and in 1972 he accepted the general secretariat of the multi-national Front for the Support of the Palestine Resistance. For the qualitative change in his political conduct Jumblatt earned the Lenin Peace Prize and the Order of Lenin from the Soviet government.

When war broke out in Lebanon in 1975 Jumblatt warned that "revolution is knocking at the door" and that it would not relent until the "decadent system is gone forever." In its place he proposed an Interim Program for Democratic Reform designed by the National Movement and calling for sweeping changes, including the abolishment of political sectarianism, restructuring the army, reinforcing democratic representation and augmenting the influence of parliament within the structure of power, and introducing "socio-economic democracy." This revolutionary course and his alliance with the radicals and the PLO, as well as his rejection of a Syrian-sponsored program for constitutional reform in February 1976, put him on a collision course with Damascus which was catastrophic for his career. Succumbing to Syrian pressure, the PLO grudgingly moved away from a badly defeated Jumblatt. On March 16, 1977, Kamal Jumblatt was assassinated while on the way to his home village, Mukhtarah in the Shouf region. His assassin's identity was not determined.

Kamal Jumblatt attended French schools throughout his academic career. He went to the Lazarist School in Ayntourah, Lebanon, for his pre-college education. In 1936 he went to Paris where he pursued his interest in the humanities in the Sorbonne. Prospect of World War II prematurely brought him back to Lebanon in 1938, where he joined the Universite Saint Joseph in Beirut and obtained a law degree in 1942. He continued his self-education in the humanities throughout his life. He was proficient in numerous foreign languages, regularly travelled to Europe and the East, practiced meditation, and was a vegetarian. Jumblatt was married to May Shakib Arslan in 1948. They separated soon after they had their first and only son, Walid, who took over leadership of the Druze during Lebanon's devastating military conflicts that ran through most of the 1980s.