Trump supporter taught 4-year-old son to racially harass their 70-year-old neighbor, according to police.

Keirian Kelly allegedly threatened to stab the black woman several times over the last three months at their downtown Cleveland apartment building, reported Cleveland.com.

The threats started in July, when the black woman said she accidentally fell into Kelly’s wife in the lobby of their apartment building.

The 28-year-old Kelly and his wife argued with the woman, and he remained angry even after the wife calmed down.

The woman said Kelly called her the N-word during the July 26 incident, and he then beat his chest and threatened to stab her.

A security guard placed him in handcuffs and called police, the website reported.

The abuse and threats continued, and the woman said Kelly coaxed 4-year-old son into calling her the N-word — which the victim said was hurtful.

Police said the neighbor was visibly shaken when she filed the latest report, which resulted in Kelly’s arrest.

Kelly was charged with ethnic intimidation, a fifth-degree felony, but he was not charged in an Aug. 10 incident involving the woman.

He allegedly crossed the street after seeing the woman out walking, and she said he again hurled racial slurs and then spat at her, before threatening to kill her and her son.