Mr Trump visited Hialeah, Florida to hold a counter-rally as the third GOP presidential primary debate was underway nearby.
During the rally, Mr Trump name dropped Republican Congressman Carlos Gimenez of Florida — but only after butchering his name on a first attempt — and was met with a wave of boos from the audience.
Mr Trump seemed genuinely surprised by the response.
"Oh! You don't like him?" Mr Trump asked.
The crowd exploded into a vocal sea of "no."
Mr Trump immediately flipped on Mr Gimenez to keep the crowd on his side.
"What's going on, Carlos, c'mon, Carl," Mr Trump said, rolling with the audience's energy. "We gotta get that straightened out. Carlos Gimenez. Really, wow. Carlos!"
It wasn't the first time this year Mr Trump's fans booed at the name of a Republican lawmaker, but it may have been the first time he was caught off guard by the response.
Earlier this year Mr Trump rallied in South Carolina, where he mentioned Senator Lindsey Graham.
“Another man who’s always there, he’s always – I’ll tell you what, when I need help [with] the left. He’s great. He’s great. And he’s my friend, too. Lindsey Graham, wherever you are, Lindsey. Thank you,” Mr Trump said during the rally.
His audience immediately turned and began to jeer the senator, though Mr Trump seemed prepared for the response, insisting to his fans that the senator was helpful when it came to winning over Democrats.
“Oh, no, no. He helps me on the left. We need help sometimes. Republicans shouldn’t need help from the left, but he helps me,” Mr Trump said.
As for Mr Gimenez, it's unclear why the crowd turned on him. The lawmaker was not at the rally that evening and was instead serving as Mr Trump's "surrogate" at the venue where the Republican presidential debate was held.
The ire from Mr Trump's supporters may be rooted in Mr Gimenez's refusal to vote against certifying the results of the 2020 presidential election. Mr Trump wrongly claims that refusing to certify the results would have provided him a path to retaking power.