"NOTE: Organizations themselves cannot contribute to candidates and party committees."

How about an actual threat, the Koch family (one of the infamous brothers died), who by themselves have a budget about the same size as the entire us republican party, and have taken it upon themselves to select the next republican presidential candidate - and they will back that up with enormous spending. Regardless of your views on the political parties specific choices, it's a bad idea for a private group to control (or credibly attempt to control) who can run for president - this is fundamentally different than microsoft's donations (even if I don't like that corporations are putting money into politics). Koch have had a lot of success in setting the previous few decade's political framework about how the us looked at international trade, along with influencing the libertarian party (David Koch was the Libertarian VP candidate in 1980, but had enormous impact on that movement over time).