It's unclear if the mayor will have a Democratic primary challenger next year, but he is already publicly clashing with one potential candidate. NY1's Courtney Gross reports on the escalating fight between Scott Stringer and the mayor. 

You could say City Comptroller Scott Stringer started it. He gave a sweeping address on Thursday slamming the mayor for not utilizing vacant land for affordable housing. 

According to Stringer, Mayor Bill de Blasio was moving too slowly to fix the city's problems. 

The mayor says otherwise. 

"It's breathtaking how little the comptroller understands about this issue," de Blasio said. "We've gone over this publicly many times."

"What's breathtaking is his haplessness in dealing with the problems facing the city," Stringer said. "I talk about issues that New Yorkers are concerned about."

This tension between the comptroller and mayor spilled into public view on Friday, fueling speculation these two could face off in a primary next year. 

Stringer's name is often floated as a potential de Blasio challenger. He has not declared what office he will seek next year. 

"Right now, the political work I want to do is to make sure Hillary Clinton gets elected president," Stringer said.

This week's dispute may have hit de Blasio's Achilles heel: affordable housing. It was about this proposal Stringer put forward earlier this year. It suggests 1,100 city-owned vacant properties be developed for affordable housing. Development, Stringer says, that needs to happen now.

City Hall argues only 60 percent of these properties are suitable for residential development. The planning for many of these sites, they say, is already in the works.

"We've made clear that there is a very substantial number of publicly owned lots that are being developed for affordable housing. There are others that physically can't be because of health or safety issues or logistical issues," de Blasio said. "You know, the comptroller is being very disingenuous. If he read any of the reports and wasn't grandstanding, it would be quite clear this is something we are already addressing."

"It's a shame that the mayor of the greatest city on earth is now reduced to these political and personal attacks," Stringer said.

Stringer certainly likes to flirt with the idea of running for mayor, but he told us he would officially decide after the general election.