Between 1985 and 2001, the organization received $9,963,301 in 73 grants from only four foundations:
John M. Olin Foundation, Inc.
Lynde and Harry Bradley Foundation
Scaife Foundations (Sarah Mellon Scaife)
Smith Richardson Foundation"
All four of these are characterized (by SourceWatch, at least, in their own descriptions linked in the above quote) as very conservative, small-government/low-regulation foundations. Actually they say the Scaife foundation is no longer pushing this ideology since Sarah Mellon Scaife took over, but (I think) during the 1985-2001 period they were. I wouldn’t necessarily trust SourceWatch on this (e.g. they say the Olin Foundation gave $20.5 million to “right-wing think tanks” in 2001, then give a list that includes the Brookings Institution. I’m fairly confident this is not a mistake, rather a combination of deadpan humor and a genuinely left-wing viewpoint that does see Brookings as part of the right-wing liberal establishment. But Olin is well known as a conservative foundation, so the characterization of Olin, if not of Brookings, seems reasonable.
Of course, that was from a 2010 article. Let’s see who funds them now.