Political Contributions: Not Philanthropy, but What Exactly?

I had never donated to a specific political campaign candidate until a few years ago. Since I am a committed voter, have volunteered on campaigns, and follow politics closely, why not? For the simple reason that no one ever asked me personally. We sent an occasional very modest contribution to the Democratic party [yes, big surprise that I am a Democrat, right?!], but that was it.
In 2004 a friend solicited us to donate to the State Senatorial campaign of a young unknown underdog, Josh Shapiro. I trust the friend's judgment, the donation was insignificant in our budget, and it made me feel good to say yes to my friend (who has said yes to things I have asked him to contribute to), even though it wasn't in my district. Not only did Josh WIN, he has already been re-elected and is a rising star in the State Legislature. That feels great! For $25, when I ran into him at a fundraiser for a different candidate, I got to tell him I was one of his backers - he even sent us a complementary 2007 calendar. Note that I actually do feel very invested in him; I am very proud of his success and I'm sure I will contribute to further war chests as he rises up the ranks. It's rather like buying a flyer stock; you feel really smart for being an early investor. So I can only imagine how the Big Donors feel when they help elect a candidate.
We did get on a list of invitees to other campaign fundraisers and decided to contribute to a bigger donor event for this past fall's congressional campaign. The reception held a room full of people who had made significant gifts to attend the event and meet and hear from the congressional candidates; I felt like I was being inducted into a secret society. I recognized a few folks from around the neighborhood, some from other donor benefit events whom I think of them as my Fundraiser Friends, since that is where we intersect. I realized I was quite the naif: obviously this is how political campaigns have always been run, but before then I had never paid enough to have access to this scene. [Once again our guy, Patrick Murphy, won. I'd say we were on a roll, but the other candidate we supported lost, as did the mayoral candidate whom we backed.]
There are campaign contribution limits which change the game some, though I don't believe there are limits on HOW MANY campaigns to which one can contribute. Volunteering is another way to contribute, of course, but donating, or donating and volunteering gains you more visibility. A willingness to lead a candidate to one's wealthy contributer friends obviously makes a person very attractive.
These are not selfless gifts. They help the candidate a donor has determined is his or her choice. Donations finance the campaign of a candidate the donor hopes will win, and then support the causes the donor cares about, some of which may benefit the donor directly. On the other hand, donor motives are not all selfish; many of those who will benefit from the candidate's decisions are people whom have no money to influence campaigns. Donors focus on every issue imaginable. It is a form of lobbying.
We have concluded that while not tax-deductible, our political campaign contributions are at least tithe-deductible! I feel a certain sense of noblesse oblige. Backing candidates, even to a modest degree, seems like good citizenship, a kind of self-tax on privilege.
But it doesn't feel like this is how democracy is supposed to work! It was heartening when a local wealthy businessman spent $10,000,000 of his spare cash to run for mayor and lost; however that was the good news. The bad news is that successful candidates have to be excellent fundraisers, period.
How do you make decisions about political contributions? What sort of priorities and budgets do you set? When you contribute, what kind of expectations do you have?