A “No Kings” demonstrator has been arrested after cops say he’s the guy who tripped a man who yelled out a gay slur at protesters in a video now going viral.

Here’s the deal … video is going around online capturing a moment from the protest that took place in Denver Saturday — where you hear a man cheering for the president while flipping off “No Kings” protesters.

His antics reach a fever pitch when you hear the man use a gay slur … yelling at someone, “Ride your bike you f***ing f**.” In the video, a young person holding a skateboard then appears to steal his glasses and tear off down the street.

You see this man give chase … and, it appears he slips and falls hard in the street — before getting back up to give chase again. After he’s run a bit farther, it looks like he’s tripped by someone and hits the ground hard.

Police say they’ve now arrested the person they believe tripped him … a 20-year-old named Jose Cardenas. They’re alleging he “caused a serious laceration” to the victim’s head.

Cops say they showed Cardenas to witnesses of the incident … and they say those witnesses identified Cardenas as the person responsible. He was taken to the Denver Jail and charged with aggravated assault.