Corruption/bribery is always a problem in politics. The US Constitution was written to grant the government limited powers; over time, explicit limits have been worn down to corrupt plain meaning of key terms ("interstate commerce", "general welfare", etc) and normalize the very perversion they were intended to prevent.

The ultimate solution to such problems remains intact: vote. Lobbying and voter persuasion is quite effective, so vote out those who create/preserve such loopholes and vote in those who close them. For all the whining consternation people exude about such problems, very few actually direct that energy toward meaningful solutions; the super rich and corporations have learned to direct such energy and exploit it accordingly.