So far every communist country (that I can think of ) has also been a dictatorship or something similar. Had there been any movements for a democratically run communist state? If there have been, why did they fail?
I'm afraid I'm not terribly qualified to elaborate on the performance of democratic communist movements and why they failed (that is, if they failed at all), but there certainly have been many of them throughout history. A famous proponent of democratic communism was Rosa Luxemburg, who along with Karl Liebknecht led the Sparticist Uprising against Weimar Germany in 1919, but were crushed by the Weimar government with the aid of right-wing paramilitaries.
Many countries have also democratically elected Communist governments in the past (by which I mean governments that actually call themselves Communist, ie. not including leftist governments in Latin America): the first being post-WW2 San Marino, but also Cyprus and many of the eastern states of India such as West Bengal.
Your premise is flawed. Every communist country I'm aware of has elections, like a democracy. Is the election of Stalin any less valid than the election of Roosevelt?