A communist party is a political party that advocates the application of the social and economic principles of communism through state policy. The name was first in the title of the 1848 tract Manifesto of the Communist Party by Karl Marx and Friedrich Engels. A communist party is the vanguard party of the working class (proletariat), whether ruling or non-ruling. As a ruling party, the communist party exercises power in the name of the dictatorship of the proletariat. The idea of communist party dictatorship was heavily influenced by Vladimir Lenin's writings about the role of the revolutionary party in the first two decades of the twentieth century when Russian social democracy divided into Bolshevik (meaning "of the majority") and Menshevik (meaning "of the minority") factions. Lenin, leader of the Bolsheviks, argued that a revolutionary party should be a small vanguard party with a centralized political command and a strict cadre policy emphasizing subservience to the party’s decisions; the Menshevik faction members like Trotsky, in contrast, argued that the party should not neglect the important role to be played by the masses in a communist revolution. The Bolshevik party, which eventually became the Communist Party of the Soviet Union, took power in Russia after the October Revolution in 1917. With the creation of the Communist International, the concept of party building was copied by emerging Communist parties worldwide. The Comintern required every one of its members to call themselves communist. They were subsequently known as Leninist or, later, Marxist-Leninist parties. The doctrine of Leninism which was popularized by Joseph Stalin in 1924 in the handbook, Problems of Leninism.
The Chinese Communist Party is the world's largest political party, holding nearly 78 million members at the end of 2009 which constitutes about 5.6% of the total population of mainland China.
The Communist Party USA is also banned in the United States under the Communist Control Act, however the Act was never enforced and the Party still exists today. Some U.S. states also have their own laws banning the CPUSA; likewise none of those laws have ever been enforced.