It started running late because I wasn't sure what the budget would look like.
However, in the first few hours, we have had:
32,634 people located in San Francisco (as determined by Facebook) see the ad
An average display frequency (number of times each sees it) of 2.9
Total displays of approximately 95,000
21 click it (0.022% click-through)
Spent a total of $17.86 -- for an average price of $0.19 per thousand displays
The display number may include some people that aren't actually located within the city, due to Facebook's geolocation fuzziness factor.
For comparison, DoubleClick estimates that typical display ad click-through is approximately 0.1%, and average rates for non-targeted political ads are lower (I don't have an exact stat). Given our demographic, I'd call the campaign a success so far.
If there are funds remaining in the budget when the campaign expires on election day, I will plan to contribute those resources to the campaign committee when it is formally established.
All in all, it seems online advertising is a fairly cost-efficient, easily-benchmarked way of reaching an audience. I'm actually quite pleasantly surprised by what we got for the dollar figure we've consumed so far.