Under cathedral ceilings and soaring stained glass windows, Garry Tan clutched a microphone as he greeted a crowd of political centrists, including San Francisco’s mayor, local prosecutors and police brass.

“Welcome to the church of turning San Francisco around!” said Mr. Tan at a fund-raiser he was hosting for local Asian American female political candidates just days before the Super Tuesday elections this month.

For a man evangelizing for change in San Francisco, owning a condo that used to be part of a church comes in handy. Last year, he scooped up the $3.95 million space near the city’s palm-tree-studded Dolores Park to hold events like this one — events he hopes will shift San Francisco from its idealistic progressivism toward nuts-and-bolts centrism.

Mr. Tan’s day job is chief executive of Y Combinator, the accelerator for tech start-ups that has helped create household names including Airbnb, DoorDash, Dropbox, Instacart and Reddit.

But Mr. Tan’s passion, as it is for a growing number of tech industry leaders, is San Francisco politics. He is one of a cadre of love-them-or-hate-them tech executives and investors with lots of opinions about the city and endless piles of cash to, as they say in the tech industry, move fast and break things. (Their critics would say it’s more like they’re trying to buy City Hall.)

To some of San Francisco’s political establishment, Mr. Tan, 43, has become the most annoying in a parade of wealthy tech executives. He has created a bombastic online persona while spending about $400,000 on local politics in the past few years — with potentially a lot more to come. And on the social media site X, where he has 425,000 followers, Mr. Tan doesn’t just rub some people the wrong way, he enrages them.