A heckler repeatedly yelled “Let’s go Brandon” as Joe Biden denounced MAGA Republicans and threats of political violence in his primetime address.
The phrase has become a Republican code for insulting the president and was shouted repeatedly as Mr Biden gave a speech on protecting democracy from Philadelphia on Thursday.
Mr Biden even joked about the heckler using a “bullhorn” and defended their right to voice their opinion.
“They are entitled to be outrageous, this is a democracy,” he said. “Good manners is not something they have ever suffered from.”
The heckling could be clearly heard on the live television feed of the speech, which was in front of Independence Hall.
“Throughout our history, Americans have often made the greatest progress coming out of some of our darkest moments like you’re hearing on that bullhorn. I believe we can and must do that again – and we are.”
During his speech, Mr Biden told the country that there was no place in politics for violence and threats.
“There are public figures today, yesterday, and the day before predicting and all but calling for mass violence and rioting in the streets. This is inflammatory. It’s dangerous,” said Mr Biden.
“I want to say this plain and simple – there is no place for political violence in America. Period. None. Ever ... we can’t be pro-insurrectionist and pro-American. They are incompatible.”
Earlier in the speech, Mr Biden had targeted Donald Trump for scathing criticism.
“Equality and Democracy are under assault. We do ourselves no favor to pretend otherwise,” says President Biden.
And he added: “Donald Trump and the MAGA Republicans represent an extremism that threatens the very foundations of our Republic.”