Beginning with Soviet occupation of Nazi-allied Bulgaria in September 1944, the political culture of that country had been totally dominated by a monolithic communist party. In the following three years, that party took advantage of the presence of Soviet troops, decades-long disorder in the Bulgarian political system, and its own high visibility as an anti-Nazi resistance force to complete a rapid communization process.

Postwar communist rule in Bulgaria can be divided into three periods with varying political characteristics. The first period, 1944 through 1947, saw the consolidation of communist power. The Fatherland Front, which began in 1942 as a small illegal antifascist coalition, led a coup that coincided with the 1944 Soviet invasion and installed communists for the first time in crucial government positions. In the next three years, the BCP gradually eliminated disorganized blocks of political opposition, cut Bulgaria off from foreign influences except that of the Soviet Bloc, and confiscated most private economic resources. By the end of 1947, the last effective political opposition had been eliminated and Soviet troops had left Bulgaria. Longtime communist leader Georgi Dimitrov was prime minister of a Bulgarian government that ruled according to a new constitution modeled after that of the Soviet Union. Although that constitution left the political institutions of prewar Bulgaria nominally intact, the consolidation period set the pattern for a very different set of political relationships. Actual political power was concentrated entirely in the national BCP. From 1947 until 1989, nominations and elections to judicial, legislative, and executive posts required party approval. During that time, a nominal second party existed, but party nominees were elected without opposition at all levels of government. The National Assembly (Narodno Subranie) met only to rubber-stamp proposals from the party or the executive branch.

The second phase of the communist period, from 1948 through 1953, strengthened Bulgaria's traditionally close ties with the Soviet Union and established a pattern of imitating the Soviet Union in all major aspects of foreign and domestic policy. The first Bulgarian Five-Year Plan began in 1949, by which time most means of production were in state hands. In 1949 Dimitrov was succeeded by Vulko Chervenkov, a protégé of Soviet leader Joseph V. Stalin. Chervenkov imitated his patron's cult of personality by assuming total control of the BCP and the government and enforcing complete conformity to party policy through 1954. Chervenkov intensified the sovietization that began under Dimitrov; the only vestiges of political diversity at this point were a few national party leaders who survived Chervenkov's purges.

In 1953 the death of Stalin brought a strong reaction in Soviet politics against the cult of personality and in favor of collective leadership. Accordingly, in 1954 Todor Zhivkov replaced Chervenkov as first secretary of the BCP. In the next eight years, Zhivkov gradually consolidated his position as supreme leader. In doing so, he maintained the totalitarian state machinery of his predecessors but showed flexibility and resiliency--especially in maintaining power at home while following the winding path of Soviet policy to which Bulgaria remained scrupulously loyal. In spite of dramatic international changes and crises between 1954 and 1989, the Zhivkov era was the longest period of stable rule by a single administration in the history of the modern Bulgarian state.

In the 1980s, however, the Zhivkov regime was overtaken by the wave of political liberation that swept all of Eastern Europe, and by the lethargy and corruption of an administration totally without opposition for nearly thirty years. Immediately after Zhivkov's fall, Bulgaria returned to its precommunist political culture, a shifting mosaic of major and minor parties and coalitions. The National Assembly was resurrected as the vehicle for democratic representation, and the first free parliamentary election was held in 1990. Unlike the communist parties of other East European nations, the BCP (which changed its name in 1990 to the Bulgarian Socialist Party, BSP) was based on a domestic political movement that predated the 1917 Russian Revolution. Partly for this reason, the BSP was able to win the first free elections that followed overthrow of the old regime. But internal fragmentation, economic crisis, and the party's connection with the wrongs of the Zhivkov era diminished the BSP's popular support as the 1990s began.

Meanwhile, based on very brief experimentation with true parliamentary democracy before World War II, and imitating its East European neighbors, Bulgaria had decisively rejected repressive one-party rule and professed allegiance to democracy. But formation of democratic institutions on the ruins of the early 1900s proved a formidable task in the early years of the postcommunist era. Coalition government, the main device of political stability in the precommunist era, functioned unevenly in solving the massive problems of the early 1990s, and the remaining power centers of the old regime hindered reform.