"Labor is prior to, and independent of, capital. Capital is only the fruit of labor, and could never have existed if labor had not first existed. Labor is the superior of capital, and deserves much the higher consideration."
Abraham Lincoln, 1st State of the Union.
Regarding any socialist tendencies of Lincoln, it is probably a stretch to say that he was an out-and-out Marxist or anything like that. To be quite frank we simply don't have a lot of his views on them beyond the above. Like most figures of his time, his politics were dominated by the issue of slavery, and even if he had lived he would still have been hyper-focused on Reconstruction. Still, it's certainly interesting to think about, considering that Marx was an admirer of his, and an open supporter of the Union's cause. Not to mention that many immigrant Germans, such as August Willich, fled the German States as a result of their being socialist or even communist in the aftermath of the failed 1848 Revolutions. Willich himself rose to be a major general, while prior to the war he openly feuded with Marx, including exchanging nasty letters, articles, and eventually challenging him to a duel, which Marx declined. Supposedly Willich saw Marx as not radical enough.