the real fun is in the disclaimer:

SF Gate polls are strictly surveys of those who choose to participate and are therefore not valid statistical samples.

Our poll software uses a variety of methods to ensure that only votes determined to be valid are tabulated. When this determination cannot be made, we may not process your vote. No actions are taken by SF Gate as a result of the polls.

So….do or do not those 57 votes represent a valid stastical sample of San Franciscans? Isn’t that how many people vote in the general election?