His famous publication, then, was based on post hoc examination of the data, made to see if anything could be salvaged from the failure of his hypotheses. Surely it's common enough to make such an examination. Ideally, the experimenter begins again with a new hypothesis but that's often not a practical possibility. It was because Fisher read him that way that he could raise the issue as a serious one. When it is recognized, however, that Mendel was reporting what was left of a failed experiment about speciation by hybridization, and that his results, even when fudged a bit, did support particulate inheritance, a different light is thrown on the issue.
Debate continues about it, however, and is likely to continue in the future.
MIT Press, 1995. The discovery of Evolution . HistPsyc Home Working syllabus D. Likely April 24, 1998.