Ken Buck couldn't remember whether the Koch Brothers had given him any money. In all, they have given him $10,000 in both of his campaigns. Maybe this screen capture from the Federal Election Commission website will help his memory.
If you doubt the authenticity of this image, then go to fec.gov and look for yourself. Click the link marked “Campaign Finance Disclosure Portal.” Then click “Graphic Data Presentations”, and then “House and Senate Map.” Choose the 2015-2106 campaign cycle. Click Colorado, then click 04 on the map. Where it says Ken Buck, click the link marked PAC. It’s on page 6.