“We’re not gonna take it anymore,” a crowd of thousands sang as Republican presidential candidate Donald Trump entered a South Carolina convention center on Tuesday night as a 1980s heavy metal song by the band Twisted Sister blared from speakers.

The billionaire real-estate developer’s packed rallies have been among the liveliest events in the long build-up to the November 2016 U.S. presidential election.

But they are increasingly becoming known for their undercurrent of aggression, which escalated into a physical altercation over the weekend when white Trump supporters attacked a black protester at his rally, to the candidate’s approval.

Out in the crowds, the mix of emotions is heady, setting a Trump rally apart from those of virtually all the other Republican and Democratic White House hopefuls. The rallies combine a gleeful rejection of establishment politics, a fear that the country is about to be transformed into something un-American, and a simmering aggression toward those who dissent from Trump’s world view.