Archive obviously from the Washington Compost, but actually raises interesting facts.

What facts are available about their relationship: Marx wrote for the NY Tribune (to which Lincoln subscribed) & Marx wrote a personal letter to Lincoln in 1864 (congratulating him on Northern Victory). Darwin also lived during this time, and introduced his theory of evolution. Were all three aware of one another?

I know that Lincoln's assassin appears to have been a mason, and that Darwin was a mason. It would seem likely, then, that Marx could have also been a mason. Was Lincoln? Were they all acting under orders?

I don't have the time, right now, to dig into this research topic, further. The line of thought seems promising.

https://www.marxists.org/archive/marx/iwma/documents/1864/lincoln-letter.htm