MANCHESTER, N.H. — A recording of Michael R. Bloomberg in 2015 offering an unflinching defense of stop-and-frisk policing circulated widely on social media Tuesday, signaling that the former New York City mayor is about to face more intensive scrutiny as he rises in the polls as a Democratic presidential candidate.

While Mr. Bloomberg apologized for his administration’s law-enforcement tactics in November just before he entered the race, he had previously spent years insisting that the policy was justified and effective, showing no indication that he had developed serious misgivings about stop and frisk. The policing tactic was used disproportionately against black and Latino people across New York City for years.

He offered a particularly blunt defense at the Aspen Institute in 2015: The Aspen Times reported then that Mr. Bloomberg said that crimes were committed overwhelmingly by young, male minorities, and that it made sense to deploy police in minority neighborhoods to “throw them up against the wall and frisk them” as a deterrent against carrying firearms.

An audio clip of those comments was posted on Twitter Monday by Benjamin Dixon, a progressive podcaster, who highlighted it with the hashtag #BloombergIsARacist.