A man was thrown out of a Donald Trump rally in Oklahoma City after being spotted wearing a shirt with the slogan "KKK endorses Trump".
The man wore a white shirt with the slogan crudely written on it, prompting chants and booing from the crowd.
Mr Trump paused, wandering up and down the stage, until security removed the man from the venue.
"In the good old days law enforcement acted a lot quicker than this. A lot quicker," the Republican presidential frontrunner told his audience after the man had left.
"In the good old days they'd rip him out of that seat so fast, but today everyone's politically correct."
Members of the KKK attended an earlier Trump rally in Nevada, where volunteers asked caucus-goers to ignore them.