“As you can see, I did nothing to lead people on, nor was I particularly happy with their chant. Just a very big and patriotic crowd. They love the USA!” Mr. Trump wrote early Saturday from his golf club in Bedminster, N.J.

The chant followed Mr. Trump’s attack on Ms. Omar and three of her fellow Democratic congresswomen of color — Representatives Alexandria Ocasio-Cortez of New York, Ayanna S. Pressley of Massachusetts and Rashida Tlaib of Michigan — in which the president called on the lawmakers to “go back” to their countries. All of them are American citizens, and all but Ms. Omar, a Somali refugee, were born in the United States.

A day after the Greenville rally, Mr. Trump, under pressure from congressional Republicans and even his own daughter, falsely claimed that he had tried to interrupt the chant, something clearly disproved by the video. Speaking to reporters on Friday, he declined an opportunity to criticize the chant, calling his supporters “incredible patriots” and saying he was unhappy that Ms. Omar “can hate our country.”

It is unclear whether Mr. Trump was aware of the background of Ms. Hopkins, who is a notorious right-wing agitator and former columnist for The Daily Mail whose attacks on Muslims in particular have largely exiled her from the mainstream news media. The White House did not respond to a request for comment.

Mr. Trump has often amplified, through retweets, the voices of white nationalists, fierce critics of Islam, conspiracy theorists and other activists and commentators from the far right. In May, Mr. Trump retweeted a conspiracy-theory account under the handle Deep State Exposed — whose Twitter profile claims 10 retweets by the president in all — that declared: “The ‘elite’ proclaim America must submit to Islam or else!!! #Trump2020.” That month he also retweeted a message ending with an A-O.K. emoji, which has become a symbol of the white nationalist movement.