WASHINGTON (Reuters) - President Donald Trump tried to distance himself on Thursday from supporters’ chants of “send her back” at a rally where he blasted Somalia-born U.S. Representative Ilhan Omar, as Republicans worry the incendiary mantra could set the tone for the 2020 campaign.

Omar, a Democrat, shot back that Trump was “spewing fascist ideology,” and Republicans expressed alarm that the inflammatory chant, building off of provocative tweets and statements by Trump, might become a theme of his 2020 re-election campaign.

“We cannot be defined by this,” said conservative Representative Mark Walker, who added that Republican leaders in the House of Representatives discussed the potential political risks at a breakfast with Vice President Mike Pence.

“That does not need to be our campaign call,” Walker said.

He and other Republicans denounced the language used by Trump’s supporters, which followed a weekend Twitter attack by Trump on Omar and three other Democratic lawmakers, all minority women, saying they should “go back” to where they came from.

All four are U.S. citizens and, with the exception of Omar, were born in the United States. Known on Capitol Hill as “the squad,” the four lawmakers are sharp critics of both Trump and the Democratic House leadership. Besides Omar, the other three are Alexandria Ocasio-Cortez, Rashida Tlaib and Ayanna Pressley.

Their physical safety and security was emerging as an issue. House Homeland Security Committee Chairman Bennie Thompson asked the Capitol Police in a letter on Thursday for an emergency meeting to discuss the president’s attacks on the four women.

“Last night at a campaign rally, the president once again used inflammatory rhetoric about the four congresswomen,” Thompson wrote, adding that the police department “must act swiftly to address heightened threats to these and other members of Congress.” It followed a similar request Thompson made on Monday.

Trump at midday tried to distance himself from the chant. At the White House, he told reporters: “I felt a little bit badly about it. ... I would say that I was not happy with it. I disagreed with it. But, again, I didn’t say that. They did. And I disagreed with.”

“TRUMP’S DEMAGOGUERY”

At the rally, Trump intensified his vilification of the four congresswomen and underscored that such attacks will be a key part of his strategy for winning re-election in 2020. He went on a 20-minute diatribe about the four women, saying they were welcome to leave the country if they do not like his policies.

When the chant started, Trump paused for several seconds and looked across the crowd silently from the podium. As the chant died down, he resumed his verbal attack.

The chanting was reminiscent of calls to “lock her up” during Trump’s 2016 presidential campaign against Democrat Hillary Clinton.

U.S. President Donald Trump speaks about U.S. Representative Ilhan Omar, and the crowd responded with "send her back", at a campaign rally in Greenville, North Carolina, U.S., July 17, 2019. REUTERS/Jonathan Drake

In remarks later to reporters, Omar slammed the president, saying, “He’s spewing his fascist ideology on stage, telling U.S. citizens to go back because they don’t agree with his detrimental policies for our country.”

Omar later on Thursday flew to Minneapolis, which along with some of its suburbs comprises her Congressional district, and was greeted at the airport by dozens of supporters who chanted “welcome home Ilhan.”

At a townhall event in Minneapolis on healthcare, she received a standing ovation and told the packed crowd: “I know there are a lot of people that are trying to distract us now. But I want you all to know that we are not going to let them.”

As of Thursday, more than 40 of the 250 Republicans in Congress had criticized Trump over his attacks.

Republican Senator Mitt Romney, asked about the “send her back” chant, said, “It’s very unfortunate for our country. ... And I’m glad the president has spoken out against it.”

U.S. Representative Justin Amash, a longtime Trump critic who left the Republican Party this month to become an independent, tweeted: “A chant like ‘Send her back!’ is ugly and dangerous, and it is the inevitable consequence of President Trump’s demagoguery. This is how history’s worst episodes begin. We must not allow this man to take us to such a place.”

The outrage capped a tumultuous Trump-dominated week that took its toll on House members.

“Nerves are frayed. People are on edge,” Democratic Representative Debbie Dingell told reporters. “The Republican caucus is at each other’s throats. We’re at each other’s throats. We need to all go home ... and listen to what our constituents care about.”