Leonard Leo-tied nonprofits have paid his businesses $90 million in just six years

Outside spending by non-disclosing groups has reached new heights in this election cycle—an unfortunate trend showing that federal agencies need to institute and enforce stricter controls.

CREW filed a complaint last week with the IRS against a nonprofit that is a supposed "social welfare organization"—and therefore doesn't have to disclose its donors—but clearly exists almost entirely to support Sen. Marco Rubio's presidential campaign.

A couple weeks ago, CREW filed a complaint against the Michigan Advocacy Trust, a secretive political organization that is spending millions of dollars on TV ads while refusing to disclose its donors—despite the fact that the law requires them to.

It's been three years since CREW filed several complaints with the FEC alleging that Murray Energy illegally coerced employees to contribute to the company's PAC and forced employees to attend a Republican presidential rally.

Following an FEC complaint about inaccurate filing, freshman Arizona Congressman Ruben Gallego settled with the organization for $2,000.