Trying to get through the lobby

If I got called on for one question of Herman Cain, he'd be psyched. Because it wouldn't be anything like what's getting thrown his way currently. My question would be one that would require no evasion and I suspect the answer would be interesting to people across the political spectrum. I'd ask about something that relates directly to his background, yet it also deals with an issue I'm beginning to wrassle. Here goes - what does a lobbyist actually do? I realize that makes me sound like I'm in elementary school. But it is for me an essential logic puzzle that just doesn't get asked enough. After all, I think one of the most misused and misunderstood terms in modern American life is "lobbying". So the idea of a "lobbyist" - whether for restaurants or agribusiness or toxic waste disposal - is the sort of Rorschach test definition that I'd love to hear offered. By Mr. Cain or any professional who did or does the job. Because the layers of that onion don't come off cleanly or in a manner that makes much sense. For example, say a particular concern pays you (the lobbyist) some money (such as $40K in 2010). It's assumed you do something for them. Obviously. Whatever that something might be, you (still lobbying) then do more work for them (now let's say $20K in 2011). Easy peasy. Except...who measures what and how? Once again, really basic stuff. I'm sure the Herminator could help me out there. Or maybe someone less, um, exposed at the moment. Whatever the angle through the lobby, my door is always open.