Fists Fly Outside Trump Rally in Michigan, Fight Caught on Video

Donald Trump's supporters seemed to forget they're on the same side ... with a group of men getting into a physical altercation at a Michigan rally for the former prez.

The Trump campaign is hosting a rally at Saginaw Valley State University Thursday afternoon, where large crowds gathered in anticipation of 45's planned address in the swing state. But, the scene outside took a chaotic turn when 3 men got into an all-out brawl in the parking lot of the university.

Watch the video ... 2 men decked out in MAGA merch pummel another attendee wearing a hat and sweatshirt supporting the former president's 2024 campaign.

The scuffle escalates as one man begins punching down on his rival's head, prompting a bystander to try to intervene. The grappling continues as one participant finds his footing, throwing a barrage of punches at his opponent.

Security finally breaks up the fight after one officer tackles a fighter to the ground, with the other 2 fended off by another guard.

Unsubstantiated reports claim the altercation was between vendors at the Trump rally ... though, it's unclear what exactly sparked the fight.

We doubt the violent outburst will deter Trump's plans to speak in Saginaw. He's set to address his supporters at 3 PM Thursday.

Vice President Kamala Harris is also expected to visit Michigan this week, but is first scheduled to appear in Wisconsin today.