US President Donald Trump has stepped up his war of words with Democrats after his spokeswoman was kicked out of a restaurant by its anti-Trump owner.
Democratic lawmaker Maxine Waters encouraged supporters to publicly harass Trump administration officials during a rally on Saturday.
On Monday, Mr Trump warned Ms Waters in a tweet: "Be careful what you wish for Max."
Top Democrat Nancy Pelosi has chided Ms Waters, as well as Mr Trump.
In his tweet on Monday, Mr Trump called Ms Waters a person with "an extraordinarily low IQ" who had "called for harm" to his supporters.
Congresswoman Maxine Waters, an extraordinarily low IQ person, has become, together with Nancy Pelosi, the Face of the Democrat Party. She has just called for harm to supporters, of which there are many, of the Make America Great Again movement. Be careful what you wish for Max!— Donald J. Trump (@realDonaldTrump) June 25, 2018
The controversy began on Friday night, when White House press secretary Sarah Sanders was kicked out of the Red Hen restaurant because of her work for President Trump.
"I have a business, and I want the business to thrive," owner Stephanie Wilkinson later told the Washington Post.
"This feels like the moment in our democracy when people have to make uncomfortable actions and decisions to uphold their morals," she continued.
At a rally in Los Angeles on Saturday, Ms Waters encouraged people to act against the Trump administration in similar ways.
"If you see anybody from that Cabinet in a restaurant, in a department store, at a gasoline station, you get out and you create a crowd, and you push back on them," she said at the event, which was filmed and shared on YouTube.
"You tell them they're not welcome anymore, anywhere," the California congresswoman said, calling for Mr Trump's impeachment during the same speech.
A respite from Washington
Analysis by Tara McKelvey, BBC White House Reporter
As President Trump walked across the South Lawn of the White House on Monday, my colleagues and I shouted questions about migrant family separations.
He gave a wave and left on Marine One, heading to South Carolina, a state he won by a landslide in 2016. It'll provide a respite from Washington - and highlights the divide between the nation's capital and the conservative political heartland.
Mr Trump will lead a rally in the state capitol of Columbia for Governor Henry McMaster - on the eve of a gubernatorial vote in the state.
As lieutenant governor, McMaster was the first state-wide official to endorse Mr Trump. Now the president is returning the favour.
Mr Trump may be under attack in Washington. In cities like West Columbia, though, he's treated as a welcome guest.
During an interview on MSNBC after the rally, Ms Waters encouraged Americans to "harass them [Trump administration officials] until they decide that they're going to tell the President, 'no I can't hang with you'".
Earlier on Monday, President Trump posted a tweet rubbishing the restaurant that threw out his press secretary.
The Red Hen Restaurant should focus more on cleaning its filthy canopies, doors and windows (badly needs a paint job) rather than refusing to serve a fine person like Sarah Huckabee Sanders. I always had a rule, if a restaurant is dirty on the outside, it is dirty on the inside!— Donald J. Trump (@realDonaldTrump) June 25, 2018
However, the Red Hen received a clean bill of health in its most recent health inspection, which noted "good food/unit temperatures" and staff with clean uniforms and aprons.
The White House press secretary meanwhile addressed the incident.
"We are allowed to disagree but we should be able to do so freely and without fear of harm, and this goes for all people regardless of politics," Ms Sanders told reporters during Monday's daily media briefing.
What's the reaction?
Ms Pelosi, who is the Democratic leader in the House of Representatives, chided Ms Waters on Twitter for her lack of civil discourse, while also calling out Mr Trump's "daily lack of civility".
In the crucial months ahead, we must strive to make America beautiful again. Trump’s daily lack of civility has provoked responses that are predictable but unacceptable. As we go forward, we must conduct elections in a way that achieves unity from sea to shining sea. https://t.co/vlpqOBLK4R— Nancy Pelosi (@NancyPelosi) June 25, 2018
Donald Trump Jr also had his say online, asking: "Does anyone reasonably believe other Democrats won't escalate this further to actual violence?"
Throwing Sarah Sanders' family out wasn't enough, the owner then stalked her to harass her at another spot! Does anyone reasonably believe other Democrats won't escalate this further to actual violence? After hearing Waters and Booker one would have to wonder if they even care? https://t.co/dhcAwgXgVk— Donald Trump Jr. (@DonaldJTrumpJr) June 25, 2018
Meghan McCain called Ms Waters' comments "absolutely insane - and extremely dangerous".
This is absolutely insane - and extremely dangerous. My father in law works in the administration, does this mean when we go out to dinner we should be ambushed?!? Don’t ever again give me any of the “when they go low, we go high” lip service. https://t.co/UF1feYT0Pm— Meghan McCain (@MeghanMcCain) June 24, 2018
But some on Twitter pointed out that Ms Waters had been perhaps irresponsible with her comments, but did not incite violence.
Maxine Waters DID NOT call for violence. This is irresponsible. We can debate the wisdom of her call to heckle and protest Administration officials in public, but let's call it what it is. https://t.co/AlaLKRVpae— Anthony Michael Kreis (@AnthonyMKreis) June 25, 2018
Democratic Senator Cory Booker said in an interview with MSNBC that he agreed with Ms Waters.
"If I saw an administrator out and about, there's nothing wrong with confronting that person," he said.
However, he encouraged people to "always lead with love".
The Red Hen controversy is not the first instance of Trump officials facing an angry public in the wake of the increasingly heated immigration debate.
On Friday, the Tampa Bay Times reported that Florida Attorney General Pam Bondi received a police escort while leaving a movie theatre after she was confronted by protesters over her healthcare and immigration views.
Last Wednesday, Homeland Secretary Kirstjen Nielsen was booed at a Mexican restaurant in Washington DC.
Department of Homeland Security employees have reportedly been receiving threats over the president's policies.
One department official said he found a decapitated and burned animal on his porch, WTOP reported.