Eugene Debs and Self-Pardons

The claim is sometimes made that Eugene Debs promised to pardon himself if elected President in 1920. (Debs ran for President from prison and was pardoned by Warren Harding in 1921). I cannot, though, find a primary source to support this claim. If anyone knows of one, I would much obliged if you would send it my way. I think it might be an urban myth.

UPDATE: The story so far is that Debs' running mate did suggest that Debs could self-pardon, but there is no indication that Debs said so. Thanks to John Martin for referring me to the comments by Seymour Stedman.