Except there are plenty of 'loopholes'.
1. Superpacs.
2. DNC Fund. (Automatically went to clinton in many cases, so it was another bucket of cash for her campaign. It should've been split evenly in the primary between her and other primary runners.
3. Promises. 'Hey larry, when you're out of congress, let us know if you want to work for our Posh lobby firm. Comfy pay and benefits'.
4. There own interests. Cheney / Haliburton. Anything about Trump.
5. Hillary Victory fund raised: $523.6M -- how many did state parties get of that?
6. There's a lot of ways to hide money. What about speaking engagements.. or other ways to 'pay' the candidate, so they can use their 'own' (but recently acquired) cash on hand? How much do the Clintons or Trumps receive to do a speaking engagement?
I don't know the answer to get rid of all corruption, but how is it that ISP's were able to give money to politicians who voted against net neutrality? INAL but here's a list:
https://www.theverge.com/2017/3/29/15100620/congress-fcc-isp...
Example: Grassley, Chuck : $135,125.
Obviously they can give money, and do to move their political aims. To say they don't means you're living under a box. Maybe if they give it outside an election term when they're not running for office? That money from ISP's should be illegal, but it isn't.