Using the same definition of "Left" as did Erik Von Kuehnelt-Leddihin.
Leftism Revisited (highly recommended)
Essentially "Left" are those certain that things would be better if we trusted more in human nature and our ability to tell right from wrong. "Right" means all those who find the "Left" project likely to cause more harm than good.
Some historical work on 1800 - 1865 mass media shows several threads of classical propaganda. Nothing worth publishing.
Using this definition "Left" includes Marius, Pelagius, Abelard, the Albegensians, Erasmus, the Hussites, Rousseau, Robespierre, Thomas Jefferson, Marx, and most of the current Democrat Party, and Rinos, amongst many others.