$55 million for conservative campaigns — but where did it come from?

A group with ties to the billionaire Koch brothers doled it out in the 2010 election cycle, but the sources of the cash remain a mystery.

WASHINGTON — The financial firepower that fueled the rise of a network of conservative advocacy groups now pummeling Democrats with television ads can be traced, in part, to Box 72465 in the Boulder Hills post office, on a desert road on the northern outskirts of Phoenix.

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