That assumes SF city politics would take over the suburbs.

The city of Indianapolis years ago merged itself with its surrounding county, to unify city and suburbs. This was instigated by the Republican suburban leadership so that the metro region would remain under Republican control. Indianapolis has been a more politically moderate city than peers as a result.

No, I'm saying that NYC is a very large city (speaking geographically, by population, or by politics). It has the super-liberal UWS and Greenwich/East Village, but also the UES, Staten Island, eastern Queens, Orthodox Jews in Brooklyn, old-line Italians in Arthur Avenue, Howard Beach, and a lot of ordinary middle-class areas. All those areas balance out the nutty leftism of other parts of the city.

San Francisco doesn't have anything like that. As the article discusses, the middle class has been fleeing San Francisco for decades. it's never going to elect a Bloomberg, let alone a Giuliani.