This issue of stop and frisk as a tool to fight urban crime came up again last night and Lester Holt weighed in as Trump fact checker saying it's unconstitutional.
There was some dispute this AM on whether Lester was right. A 1968 SCOTUS case, Terry v Ohio, established that officers can stop and frisk if they have a reasonable suspicion a crime is imminent. The notion became widespread under Mayor Michael Bloomberg and a judge ruled the application (widespread) was unconstitutional but Terry v Ohio was not overturned.
That case was appealed and the appeal was dropped when Mayor DiBlasio took office.
There were a couple times Mr. Holt tried to fact check Mr. Trump and I am not sure it was accurate.