Led by influential industrialist brothers Charles and David Koch, the Koch network is made up of the wealthiest conservative families, philanthropies and conservative advocacy groups. Membership requires a payment of at least US$100,000 (S$134,000) per year.
The sprawling 700-member political donor network, which is active in six competitive Senate races, has spent US$21 million on paid ads and has reservations for at least US$20 million more.
The operation is now on track to invest US$750 million in the 2016 cycle, officials said. In addition, its groups together have 1,600 staff deployed across 38 states - a political infrastructure that rivals that of the US' two main political parties.
REUTERS, BLOOMBERG, WASHINGTON POST