Was the Communist Manifesto believable?

Given the influence Karl Marx and sometime collaborator Friedrich Engels had on the theoretical evolution of revolutionaries during the first-half of the twentieth-century, it would be difficult to argue that The Communist Manifesto was not considered credible and, as an extension, believable. The Manifesto was widely circulated in revolutionary circles in Russia and Lenin and Leon Trotsky, perhaps the two of the most influential political theorists of their era, were explicitly indebted to the writings of Marx, especially Kapital and the Manifesto. Whereas Kapital was a protracted theoretical treatise, however, The Communist Manifesto was a more concise and immediate call to action. Evidence of Marx’s influence on key figures in revolutionary Russia and China include the following quotes by Lenin, Trotsky and Mao:

The Marxist doctrine is omnipotent because it is true. — Lenin, The Three Sources and Three Component Parts of Marxism (1913)
Russia achieved Marxism—the only correct revolutionary theory . . . . — Lenin, Left-Wing Communism: An Infantile Disorder (1920)
The essence of Marxism consists in this, that it approaches society concretely, as a subject for objective research, and analyzes human history as one would a colossal laboratory record. . .Precisely this objective approach arms Marxism with the insuperable power of historical foresight.— Trotsky, Dialectical Materialism and Science (1925)
The force at the core leading our cause forward is the Chinese Communist Party. The theoretical basis guiding our thinking is Marxism-Leninism. — Mao, Opening address at the First Session of the First National People's Congress of the People's Republic of China (September 15, 1954).

This attests to the importance and, hence, believability of the writings of Marx. How influential or believable is or was The Communist Manifesto is difficult to quantify. Das Kapital is frequently cited by intellectual theorists. The Manifesto is a much more popular document because it is a much briefer and strident call to action. It is held high by aspiring revolutionaries perched atop platforms and required reading in college classes across much of the world. How believable is this document is entirely dependent upon one’s own perspective. What is known for a fact is that millions of communists have referenced it and quoted from it. That suggests that is a believable document.