Koch-backed political coalition, designed to shield donors, raised $400 million in 2012

The political network spearheaded by conservative billionaires Charles and David Koch has expanded into a far-reaching operation of unrivaled complexity, built around a maze of groups that cloaks its donors, according to an analysis of new tax returns and other documents.

The filings show that the network of politically active nonprofit groups backed by the Kochs and fellow donors in the 2012 elections financially outpaced other independent groups on the right and, on its own, matched the long-established national coalition of labor unions that serves as one of the bigg