GOP strategist Karl Rove has relied largely on anonymous donors to fuel his Crossroads organizations and their attack ads targeting President Barack Obama.

To date, Rove’s Crossroads GPS and American Crossroads have spent a combined $174.3 million, with more than 70.5% of this money coming from undisclosed contributors.

American Crossroads, as a super PAC, is required to identify its donors, but not necessarily before the election. It has doled out $44 million to defeat Obama. But Crossroads GPS is classified as a non-political “social welfare organization” and is therefore not required to reveal its donors. Crossroads GPS has so far spent $123 million attacking Obama and other Democratic candidates.

Virtually all of the Crossroads funding has gone towards negative advertising (99.3%), according to the Sunlight Foundation.

The two Crossroads organizations have done so well in terms of fundraising that they have outspent the pro-Mitt Romney super PAC Restore Our Future by two-to-one, and could wind up spending more than the Republican National Committee.

The Sunlight Foundation reports that the Crossroads network originally planned to raise $240 million for this election, and that they might be “within striking distance” of this target.

Some may wonder why a campaign contributor would want to remain anonymous. One reason is that donors sometimes receive negative publicity. Others may give to one candidate, but hedge their bets by remaining anonymous in case the other candidate wins.

-Noel Brinkerhoff, David Wallechinsky

To Learn More:

American Crossroads & Crossroads GPS spend $174 million; 70% from Anonymous Donors (by Alex Engler, Sunlight Foundation)

Restore Our Future, Inc. (Sunlight Foundation Reporting Group)

American Crossroads (Sunlight Foundation Reporting Group)

Appeals Court Approves Secrecy for TV Political Ad Donors (by Noel Brinkerhoff and David Wallechinsky, AllGov)