The city's teachers' union is backing Mayor Bill de Blasio in his re-election fight as de Blasio clashes with a potential rival over body cameras. NY1's Grace Rauh filed the following report.

With the Democratic field for mayor largely to himself, Mayor Bill de Blasio is racking up some big endorsements. 

The city's teachers' union, a powerful force in local politics, announced that it is backing him for re-election.

"This is one big strong union that is organized, that reaches every neighborhood in New York City and has the respect of New Yorkers," de Blasio said.

His presence at the union headquarters, though, raised questions about why the mayor has not done more to show he is in command ahead of Thursday's snowstorm.

He missed a news briefing about the rough weather, letting top aides speak about the city's preparations. And he darted out of the teachers' union event without a word about city schools, which he announced minutes later on Twitter would be closed.

De Blasio, meanwhile, is clashing with a potential Democratic challenger, City Comptroller Scott Stringer, over body cameras for police officers. The city says it is moving forward with its $6.4 million contract to purchase up to 5,000 body cameras, despite objections by Stringer.

Last week, the comptroller refused to sign off on the contract. A source said he declined after learning that the Department of Investigation is investigating the agreement. The mayor fired back after Stringer refused to sign off, without disclosing that the contract was under investigation.

"It's unfortunate that the mayor decided to play politics and talk about different issues, but nothing about the DOI investigation. That's the way he chooses to do business. But as comptroller, it's my job to go through all the due diligence we need to do," Stringer said.

Stringer did officially register the contract on Wednesday. An aide says the office was essentially forced to by the city.

Then, there's the mayor's upcoming meeting with federal prosecutors. A source tells NY1 the sit-down will take place in Midtown at the offices of the mayor's lawyer and not at the U.S. attorney's headquarters in Lower Manhattan.