Psychology of campaign donations: reverse-causation giving

I made my first donation to Obama's reelection campaign more or less when first asked, in February 2011, and doled it out in gradually accelerating dribs and drabs as campaign season kicked into gear, keeping a rough count in my head -- corrected and ratified, starting I think this past August, with occasional emails from the campaign spelling out the total.  I went from about once a month to twice a month to 3x at the end, and I let various moments of personal anxiety or perceived need (almost never induced by the 20 emails a day I was getting) spike it.

As with voting, if you're not a megadonor you know your money won't make a measurable difference -- my $100 won't make a dent in the $10 million Super PAC buy I just read about. So why do it?   The simple answer is you do what you can and hope others will too -- but over time I noticed a slightly magical element to that. It seems I was acting on a kind of reverse causation assumption: that I was part of a kind of herd mind, and that if I decided to donate at a particular moment, it was a good bet that others would too. So I could make it happen by letting it happen.