Nearly 90 percent of the spending by these nonprofits — more than $84 million — came from groups that never publicly disclosed their funders, the joint analysis of Federal Election Commission data found. Another $8 million came from groups that only partially revealed their donors.
Unlike the nonprofits, super PACs are required to release the names of their contributors.
In terms of party allegiance, conservative “social welfare” groups outspent liberal groups $78 million to $16 million, nearly 5-to-1, according to the analysis.
So far in the 2012 election cycle, super PACs have far outspent nonprofits, thanks mainly to candidate-specific committees that were active during the GOP primaries. Super PACs have spent more than $120 million compared to about $9 million by 501(c)(4)s. But with clearly defined candidates for both the White House and in most congressional races, nonprofits are expected to become more active.