It appears that the Franc data on how working-class donors favor the GOP was drawn - appropriately enough - from Arianna Huffington's Fundrace 2008 page.
Update: Frequent commenter DivGuy writes:
Franc's analysis of 2008 presidential donors is fatally flawed because the FEC only requires the disclosure of personal information for donors who give more than $200. You can see this quite easily by searching the site for any name or city, and you'll find that all are people who gave in excess of $200.
Barack Obama has received at least 80% of his donations (43% of his total funds raised) from small donors who gave less than $200 and who are not listed in the FEC database, or on the HuffPo site that uses the FEC data.
For instance, Franc said that Republicans had more contributions from waitresses. If you search for "waitress", you'll only see 30 donors - that's obviously far too few, and should have tipped Franc off to the incomplete nature of the data ... Not only that, but of the 14 waitresses who gave to Republicans, 13 gave to Ron Paul.