Public Advocate Bill de Blasio is expected to make his mayoral campaign official on Sunday.
He will make the announcement in front of his home in Park Slope with his family.
De Blasio was elected public advocate in 2009 and before that, he served in the City Council.
He will be running in the Democratic primary.
So far, former comptroller Bill Thompson and former City Council member Sal Albanese have declared on the Democratic ticket, while former MTA Chairman Joe Lhota and newspaper publisher Tom Allon have announced they are running for mayor as Republicans.