William Blake's political views, much like his religious views, were outside of the traditional mold. He championed change and revolution. He lived during the French Revolution of the 1790s, which shook up the whole of Europe with its massive overhaul of the monarchy in favor of a more democratic system (though he later became disenchanted with the revolution, feeling it replaced one system of tyranny with another).
He was also sensitive to the plight of the poor and underprivileged classes. His Songs of Innocence and Experience depict orphaned children being forced to work as chimney sweeps, often dying young. He also opposed slavery.
Blake distrusted the monarchy and organized religion. He was in favor of sexual freedom. Basically, he was the ultimate individualist, and this is reflected in his politics, which are hard to pin down under simple labels.