Asked several times by reporters why he didn't stop the chant, Mr. Trump said it was a 'packed arena,' very specifically saying he did not endorse the message against Omar.
"I was not happy with it," the President added. "I didn't like that they did it."
Here was the moment the chant started during his rally, in response to his criticism of four minority women Democratic House members, including Omar:
On Capitol Hill, a number of Republicans expressed their concern about the message from the Trump crowd.
"No American should ever talk to another American that way," said Rep. Tom Cole (R-OK).
"That's a very inappropriate sentiment in this country," Cole told reporters just off the House floor.
“The tweet was wrong & the chant last night grotesque,” wrote Sen. Marco Rubio (R-FL) on Twitter.
“What I’m hearing from Capitol Police is that threats are up across the board for all members,” said Rep. Mark Walker (R-NC), who expressed his concern about the ‘send her back’ chant just a few hours after the rally had ended.
As for Omar, she met on Thursday morning with House Speaker Nancy Pelosi, as reporters pressed her to respond to the chant.
“We have said this President is racist,” Omar said as she walked from the Capitol back to her House office.
Democrats said they were concerned about Omar’s safety and possible threats against her.
Rep. Hakeem Jeffries (D-NY), the head of the House Democratic Caucus, encouraged lawmakers and the Capitol Police to quickly share any information about threats to police back in their home districts.
“We got to make sure every single person, Democrat, Republican, progressive, conservative, the left and the right, get through it together,” Jeffries said.