i think the way lobbying works here is that corporations/special interest groups will make donations to a politician's campaign fund with the implication that politicians will vote favorably for said corporations/interest groups. Like the National Rifle Association donating to a politician and then saying "Hey there's a big vote on gun control laws coming up, it'd be a shame if we had to pull our future donations from your campaign if legislature favorable to our cause failed to pass." Politicians are given gifts, not technically payment for services/goods. This is kind of how I understand it. I might be completely wrong, though, so I'd take this with a grain of salt. I'm on mobile so I apologize for spelling and formatting errors.