David Brock, recently described by Politico as “the Democrats’ dark-arts master,” has some explaining to do. Brock is Hillary Clinton’s attack dog and has launched his own Koch-brothers-like donor network to finance attacks on President-elect Donald Trump and to rebuild the political left after Trump’s stunning victory over Clinton late last year.

Brock — a self-described right-wing hitman-turned-Clinton enforcer — has used his relationships with some of the left’s deepest pockets to build an armada of aggressive political outfits that have become pillars of the institutional left and that raised a combined $65 million during the 2016 cycle.

According to information from thecitizensaudit.com, David Brock’s organization, Media Matters for America, has failed to report to the IRS over $1 million in sublet rental income from 2010 to 2014.

In addition, David Brock and his allies are most likely pocketing that money for themselves.