Invalid assertion. But good you are thinking, but adjust it to plausibility here:
http://www.freerepublic.com/focus/news/3458886/posts?page=55#55
It’s worth further discussion as to how it could have been carried out, and how many or few it took, that’s for sure.
But, it would be easy enough to backtrack whether or not it took place. Just ask a few hundred Dem primary voters in each contested area where they went to vote. If two in a given precinct went to different places, that enables the list to be reconstructed.