Video paid for by 'social' welfare' nonprofit.

Underwriters of attack ads can easily avoid being named.

Democrat Steve Bullock's gubernatorial win a low point for litigious conservative group.

Questions raised about whether nonprofits like Koch-connected American Future Fund are primarily about politics.

Law says groups like Americans for Job Security cannot make politics its primary purpose.

Obama's new nonprofit does not intend to disclose all information it collects from donors.

IRS accused of singling out conservative groups; claims of overwork may have merit.

IRS employees routinely open wallets for Democratic candidates and liberal groups.

'Tea party'-branded nonprofits at heart of IRS scandal rarely endorsed political candidates.

The names of most social welfare nonprofits don't contain overtly political words.