Only 12% of voters vote for the right wing party in SF. How much more one-sided to the left could a place get?
The Democrat party is barely a left-leaning party. You have famous national examples like AOC and Bernie who are very progressive, but by and large, most Democrats are happy to accede to corporate power and regressive policies when it actually matters. What is considered "radical left" here in America is basically centrist by the standards of the rest of the world.