[riizade]

1912-1964 Republicans may not have been particularly right wing.

My understanding is that prior to the "Southern Strategy" (https://en.wikipedia.org/wiki/Southern_strategy) of the 1960s, the Democratic Party was largely right wing, and the Republican Party was largely left wing.

So San Francisco flipping from Republican to Democrat aligns pretty much squarely with the change in politics of the parties due to the Southern Strategy.

This implies that in fact, San Francisco has always been fairly left-wing.