Regarding candidates that refuse to accept corporate, PAC, or lobbyist money. 

What specifically does this mean? For example, how does one distinguish between a donation from a lobbyist and another one from an employee? How does one stop influence, for example, by a company subtly or not so subtly suggesting to many of its employees to donate to a particular candidate?

Finally, is there a such thing as a "local PAC"? Such as an organization whose membership is exclusively constituents of a congressman? If this kind of organization does exist, then is there something inherently wrong with accepting donations from it? (Perhaps aside from the fact that it simply blurs the lines and makes things too complicated.)

Thanks.