An interesting question: Do we know how many votes Debs (or other Socialist or minor party candidates) really got? Of course that is sometimes asked of major parties as well, but at least those have some--even if not always adequate--ways of checking that they won't be undercounted (poll watchers, etc.) and besides, it seems plausible that frauds by each major party would cancel each other out. But there is or at least was very little standing in the way of discounting votes for minor parties:
"Yet there was considerable evidence that a proper count would have come closer to the two million votes [for Norman Thomas in 1932 instead of the 884,885 recorded--DT] predicted by *Literary Digest* and others. One piece of anecdotal evidence came from a Socialist poll watcher in Chicago who called out the throwing away of ballots marked for the Communists, prompting an embarrassed response, 'When you Socialists have no watchers, we do the same to you.' David Shannon validates this view, arguing that one of the party's greatest failings was only having poll watchers in its most formidable local machines, speculating that their presence might have made the difference in electing a number of congressmen in the 1910s..."
https://books.google.com/books?id=MnflBgAAQBAJ&pg=PA327
(This is from the recent *The Socialist Party of America: A Complete History* by Jack Ross, a sometimes strange book--as one might expect from someone who once had a blog entitled "The Brooklyn Copperhead"--but the only comprehensive history of the party we have. See
http://www.dailykos.com/story/2015/...Socialist-Party-of-America-a-Complete-History for a review.)
Another bit of evidence: in 1908, "No votes for Debs were recorded in his own precinct in Terre Haute, even though he voted there and was assured of the votes of many of his neighbors." Ross, p. 109.
"The official count of the Terre Haute vote gives no vote for Debs in his own precinct, He says that both he and his brother voted the straight socialist ticket and that he knows of others who voted the ticket in that precinct. Voting machines were used."
http://archives.chicagotribune.com/1908/11/06/page/3/article/debs-denies-decline-in-vote
https://l.facebook.com/l.php?u=http...ticle/debs-denies-decline-in-vote&h=OAQEu2vR_