The original source was Powell.
"By April 11, his mind was made up. After to listening to Lincoln speak from the balcony of the Executive Mansion on his plans for reconstruction, Booth--according to Thomas Eckert who interviewed Powell in prison--turned to Lewis Powell and said, "That is the last speech he will ever make!" By April 13, Booth was casing both Ford's Theatre and Grover's National Theatre, anticipating that the President would soon take a night out--his last."
http://www.law.umkc.edu/faculty/projects/ftrials/lincolnconspiracy/lincolnaccount.html
You have put a tremendous amount of effort into a small facet of the story. Booth was present at President Lincoln's 4/1/65 speech where he advocated voting rights for blacks. It is admittedly hearsay from Eckert that Powell said that Booth said, "This means nigger citizenship." But there is no doubt that Booth did shoot President Lincoln three days later.
This touches upon the techniques of historiography. Both Dr. McPherson and Dr. Oates accept the story of Powell's. You don't. Of course you don't have to. Others will.
Walt
Then McPherson and Oates accept a third-hand account from a biased source and present it as fact.
You accept it as fact, which hardly jives with your refusal to accept multiple first-hand accounts wrt the Butler deportation meeting.
McPherson is not a credible historian. Oates' Lincoln biography is a bit better, though it too is overly worshipful of Saint Abe and riddled with errors on many of the small details. But as always this comes down not to a test of which authorities you claim but rather your own consistency in the matter, Walt.
As others have pointed out you adamantly refuse to believe Ben Butler's first hand account of a colonization meeting with Lincoln yet you'll accept third hand hearsay from Booth without question. If we were to use the court of law test, Butler would be allowed to testify. A third person recipient of Booth hearsay would not.
[Walt lying] "The original source was Lewis Powell."
[Walt's cited source for this lie:]
An internet article The Trial of the Lincoln Assassination Conspirators, by Doug Linder (2002). The web address goes to the faculty of the University of Kentucky, the academic home of none other than Edward Steers, Jr.
By April 11, his mind was made up. After to listening to Lincoln speak from the balcony of the Executive Mansion on his plans for reconstruction, Booth--according to Thomas Eckert who interviewed Powell in prison--turned to Lewis Powell and said, "That is the last speech he will ever make!"
I stated it correctly, as did Edward Steers. The original source of the fairy tale is Thomas Eckert, speaking in 1867.
The only evidence of any such statement by Paine, Payne, Powell, or whoever he was, is the unsubstantiated claim made by Thomas Eckert long after "Powell" was dead and buried.