About a week ago, a super PAC bankrolled by a wealthy conservative donorannounced that it would run an ad attacking Sen. Bernie Sanders (I-Vt.) for being too far along the ideological spectrum.

The group, called ESA Fund, was reportedly backed by $600,000 in spending from TD Ameritrade executive Joe Ricketts. And its ad went after Sanders for supporting things like free college tuition, Medicare for all and tax hikes on the super rich.