The costume came out during the Mount Pleasant Annual Halloween Parade ... and, showed a group of dudes on a golf cart impersonating Secret Service -- with one dressed up as Donald Trump.

A fake machine gun was mounted to the roof of the cart ... which all might've been fine -- except, behind the cart, a person outfitted like Kamala Harris had their hands tied by a rope connected to the cart and was slowly walking behind the vehicle.

One of the parade attendees -- Josh Huff -- says the float doesn't reflect well on the town ... and, he thinks someone high up in politics needs to make a statement to get actions like this to stop.

As for how the float got into and stayed in the parade ... Mount Pleasant's Volunteer Fire Department copped to the incident -- apologizing that the float made it in, and saying it does not reflect the organization's beliefs.

"We do not share in the values represented by those participants, and we understand how it may have hurt or offended members of our community."

In the statement, Mt. Pleasant's VFD says it usually only provides security and safety logistics for the event ... but, it will now review its planning process to stop a costume like this from getting into the parade again.