A San Francisco measure on the ballot in November caused a stir among the tech elite on Friday.

Proposition C would tax the largest businesses in the city to fund homelessness services. It could bring in $250 million to $300 million in revenue annually.

Salesforce CEO Marc Benioff is a strong proponent of the measure.

Twitter CEO Jack Dorsey used his social network on Friday to oppose Benioff's support, though Benioff was quick to respond.

Two of San Francisco's most powerful tech CEOs publicly locked horns on Friday over a measure that would make the city's largest businesses pay a greater share of the bill for homelessness services.

In a series of tweets, Salesforce CEO Marc Benioff and Twitter CEO Jack Dorsey debated Proposition C, a measure on the ballot for voters in the city in the November election that would raise taxes on large companies to help San Francisco deal with an intractable homelessness problem.

Benioff, who founded and runs the largest company in San Francisco, has endorsed Prop C, though it could ultimately cost Salesforce millions of dollars in city taxes. Benioff has issued a statement on Twitter and bought ads supporting the measure.

But Benioff's advocacy for Prop C took an unexpected twist on Friday when Dorsey, the cofounder and CEO of Twitter, responded to a Benioff tweet to explain why he opposes the measure.

"I want to help fix the homeless problem in SF and California. I don’t believe this (Prop C) is the best way to do it," Dorsey said, adding that he supported San Francisco Mayor London Breed and California state Sen. Scott Wiener's "commitment to address this the right way."

"Mayor Breed was elected to fix this," Dorsey added. "I trust her."

That set off a back-and-forth of at times testy tweets thoughout the day that attracted other tech figures, such Patrick Collison, the Irish CEO of online payment company Stripe, who voiced support for Dorsey.

The exchange highlights what has become a thorny and embarrassing problem for San Francisco, where the sight of tents, human waste, and indigence is a jarring contrast to scooter-riding techies who work for some of the most valuable companies in the world.

Twitter has been a long-standing target of criticism because several years ago it negotiated a controversial tax break as an incentive for it to remain in San Francisco and move into its Market Street headquarters.

"How much have you given?"

San Francisco's Mayor Breed, who was elected in June, has expressed opposition to Prop C. In a statement earlier this month, she said the city should do an audit of what it's already spending on homelessness services "before we double the tax bill overnight."

The San Francisco Controller's Office estimates that the tax would bring an additional $250 million to $300 million in revenue for the city each year and affect 300 to 400 local businesses; it would apply to those with more than $50 million in San Francisco gross receipts, as well as companies headquartered in the city.

Benioff responded sharply to Dorsey, suggesting the Twitter CEO was not doing his part to curb homelessness.

"Which homeless programs in our city are you supporting?" Benioff said. "Can you tell me what Twitter and Square & you are in for & at what financial levels? How much have you given to heading home our $37M initiative to get every homeless child off the streets?"

Dorsey then accused Benioff of "distracting."

By Friday evening, the two tech bigwigs had apparently had a phone conversation (Dorsey tweeted a screenshot) in an effort to patch things up.

Here's the full exchange:

On Friday evening Dorsey tweeted screenshots of his phone calls to Benioff, saying that they were now "aligned to fix this issue.":