Perhaps it's a case of projection. Perhaps the GOP knows about the fraud that they are carrying out, so they presume that Democrats must be doing something similar. Nonetheless, when it comes to voter registration fraud, Republicans are the champs, hands down. And it remains to be seen how wide and how high this story will go. This one may have legs.
As to actual voter fraud, it's Republicans --- and very high profile ones at that, including Mitt Romney himself --- who are winning that contest as well. See our recent report detailing 10+ recent cases of voter fraud and other related election fraud crimes by very high profile Republicans right here.