I don't believe he'll find any. It's a "factoid." Unless somebody else out there can do a Lexus/Nexus search or produce a GOP press release where some kind of credible poll data can be cited... then I will believe that that "white Christian conservative's aren't in our corner any more" crack was a sop to the minorities that the GOP has been salivating over since the Bush win. As you pointed out, Rove didn't finger conservatives in general, he fingered white Christians. It's de rigeur for liberals to finger white Christians these days. Shame on the republicans for jumping on that bandwagon.
Damnation, Harrison. Give the man a CHANCE to find his supporting data! ;^)