You could probably do it cladistically too. Sorel blasts Jaures as a social democrat (which AFAICT he was) in Reflections on Violence, but Jaures read and was influenced by Marx.

On the other hand, Social Security was explicitly inspired by Bismarck's successful attempt to buy off the socialists... but on the other other hand, many political figures at the time, including some in high places in FDR's administration were, well, not entirely unsympathetic to the Soviets.

Marx certainly wasn't a liberal, but many liberals have been influenced by people and movements far to the left of them; it could be argued (though I'm not good enough at history to argue it well) that the oppressor/oppressed mindset is one such influence.