New surveillance footage shows the still-at-large mumbling maniac who allegedly punched a 44-year-old Harlem Hospital pediatrician — sending him tumbling onto the subway tracks nearly a month ago.

The brief clip, released by the NYPD Thursday, shows the brute suspected of slugging the doc on the northbound 1 train platform at 50th Street the evening of Aug. 9.

The elusive attacker is shown strolling on the sidewalk wearing a backwards cap, white T-shirt and black shorts and carrying a backpack. 3

The suspect muttered something indecipherable before slugging the victim, a complete stranger, around 7:50 p.m., causing him to fall onto the roadbed, cops said.

Bystanders helped the bruised-up man back up onto the platform and he was hospitalized in stable condition.

The victim’s fri

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