All political movements at their core face an internal tension between conflicting tenets of their ideology. 19th century liberalism was split between its commitment to universal suffrage and the fear that the unwashed majority might use their votes to infringe on the property rights of the propertied. Even the Republican party, famous in recent years for iron discipline, is divided between cultural conservatives who would like to abolish gay people, and business conservatives who are happy to sell to gay people.
Within the broad left in the U.S, our divided dreams have often found us torn between our hope that economic planning might restore some democratic sovereignty over the anarchy of the market, and our belief that public provision of social goods was necessary for economic security.
However, I think this was a false choice, and that the progressive movement can learn much if it avoids such a division in the future.