It existed at least since 1908, so if it's fake, it's a very old fake, and written at a time when many of the people who knew Lincoln were still alive.It would seem to me that claim that it is from a letter to Elkins ought to be verifiable.
The gold standard is the nine volume Collected Works of Abraham Lincoln, edited by Roy P. Basler. It has never been shown to have included a bogus letter attributed to Lincoln. It excluded the supposed letter from Lincoln to Elkins.
It has been repeatedly debunked since the 1880s and is a famous Lincoln fraud.
Asserted quote:
I see in the near future a crisis approaching that unnerves me and causes me to tremble for the safety of my country. . . . corporations have been enthroned and an era of corruption in high places will follow, and the money power of the country will endeavor to prolong its reign by working upon the prejudices of the people until all wealth is aggregated in a few hands and the Republic is destroyed.
It was included by Emanuel Hertz in his book, Lincoln, A New Portrait at pp. 954-55.
Yes, we may all congratulate ourselves that this cruel war is nearing its close. It has cost a vast amount of treasure and blood. The best blood of the flower of American youth has been freely offered upon our country's altar that the nation might live. It has been indeed a trying hour for the republic; but I see in the near future a crisis approaching that unnerves me and causes me to tremble for the safety of my country.As a result of the war, corporations have been enthroned and an era of corruption in high places will follow, and the money power of the country will endeavor to prolong its reign by working upon the prejudices of the people until all wealth is aggregated in a few hands, and the Republic is destroyed. I feel at this moment more anxiety for the safety of my country than ever before, even in the midst of war. God grant that my suspicions may prove groundless.
That is all of it in the source relied upon by The Lincoln Encyclopedia. The entry includes neither sender, nor addressee, nor date.
Well then the guy who said he had "verified" it, did not actually do a very good job verifying it.
Still, "historians" discount the claim by Ward Hill Lamon regarding Lincoln writing out an arrest warrant for Chief Justice Taney.
Back when I was looking for it, I found three references to Lincoln ordering Taney to be arrested.
I think "historians" simply don't want to report anything about Lincoln that doesn't support their narrative.
Maybe the quote is fake, but i'm not convinced it has been mythbusted yet.