Marx and Engels begin The Communist Manifesto with "A spectre is haunting Europe" because they wanted to warn the bourgeoisie and the elite class that their movement is strong and it is not going to stop until Europe is classless. Literary effect: the movement is mainstream. Political effect: the movement is powerful.
Of course not. It is just a literary figure. What they meant is that the ideas of communism had been spreading throughout Europe and this caused fear and rejection from the traditional establishment everywhere.
