Republicans who attack the Democratic presidential candidate Kamala Harris as a San Francisco radical who is responsible for the destruction of the city must be unfamiliar with the species. Ms. Harris, who cut her teeth confronting murderers and rapists, left the city at least a decade ago.

What Republicans also don’t understand and perhaps would prefer not to admit is that there have long been two species of San Francisco Democrats. There are those like Ms. Harris, who balance a desire for social change with a practical understanding of what is achievable. And then there are the others, a generation of local politicians who have burrowed themselves into the city and used its resources to execute their devotion to a polarizing ideology that embraces a knee-jerk opposition to progress, a deep-rooted antipathy to many forms of law enforcement and a belief that higher taxes are a cure for all evil.

It is under the thumb of these local politicians that San Francisco became the poster child for much that ails the major cities of the West. And this fight isn’t just about San Francisco. It is increasingly apparent that some of our country’s most intractable problems are rooted in municipalities. It is only by shining a light on what happens in these places, on issues like affordable housing and efficient government, that we can start to design a better future for everyone.

After decades of unilateral rule, the city is undergoing a seismic shift. Democrats like me, fed up with the damage wrought by years of preposterous and overly progressive policies, are fighting to take the city back. And while most Americans will be focused on another election happening this November, many San Franciscans will also be closely watching the results of a bitterly contested mayoral race, on which the city’s future teeters.

One mayoral candidate is Aaron Peskin, one of the city’s two most powerful politicians. If you want to understand how the city got to where it is today and why it is at the center of a struggle over its future, you should take a closer look at Mr. Peskin’s long career.

Changing a deeply entrenched system is tough. As I’ve become increasingly involved in San Francisco, the city I have lived in for more than 40 years, I came to realize that Mr. Peskin and I represent clashing visions for the city’s future. TogetherSF Action, a political advocacy group I co-founded, backs Mark Farrell, one of the moderate rival Democratic mayoral candidates. (I also recently donated $500,000 to a committee that Mr. Farrell started to back a ballot measure.)