Contrary to a popular myth, Abraham Lincoln never corresponded with Karl Marx.

But Friedrich Engels absolutely was pen pals with Werner Sombart, later a principle philosophical architect of National Socialism and the Third Reich ;-)

https://www.marxists.org/archive/marx/works/1895/letters/95_03_11.htm?fbclid=IwAR17okHHnQjN-b4h39TUSsfLRWslqTZl-x7yRXtA1fvrVwrXlUQPvjC2xfY">https://www.marxists.org/archive/m...

Abram L. Harris in 1942, cutting to the core of what Sombart& #39;s 1934 book Deutscher Sozialismus was all about...

Harris further characterized Sombart& #39;s National Socialism as a school of thought defined by its "antilibertarianism" and repudiation of 19th century liberalism.

And here we have where Marx still clearly fits into the picture for Sombart as he& #39;s making his leap into Nazism, as per Harris& #39;s conclusion:

1936 article about how the Nazis were using Sombart& #39;s philosophical treatises to deify Hitler and the institution of the Fuehrer: