Democratic presidential candidates , led by Bernie Sanders and Elizabeth Warren, spoke out forcefully in defense of Rep. Ilhan Omar this weekend, after the president of the United States risked inciting violence against the Muslim congressperson by endorsing the false claim that she downplayed the September 11, 2001 terrorist attacks.

Ilhan Omar is a leader with strength and courage. She won't back down to Trump's racism and hate, and neither will we. The disgusting and dangerous attacks against her must end.

The President is inciting violence against a sitting Congresswoman—and an entire group of Americans based on their religion. It's disgusting. It's shameful. And any elected leader who refuses to condemn it shares responsibility for it.

Those comments from the progressive Democratic senators contrasted sharply with House Speaker Nancy Pelosi’s initial failure to even mention that Omar, whose life has recently been threatened by a Trump fan, was the target of the president’s inflammatory tweet , which mixed video of her with harrowing images of the World Trade Center towers falling.

As we visit our troops in Stuttgart to thank them and be briefed by them, we honor our first responsibility as leaders to protect and defend the American people. It is wrong for the President, as Commander-in-Chief, to fan the flames to make anyone less safe.

After a wave of criticism for those tepid remarks — which seemed to endorse the claim that Omar had somehow erred in failing to show “reverence” in how she referred to the 9/11 attacks — Pelosi called on Sunday for Trump’s tweet to be deleted and asked for security to be stepped up for Omar.

. @realDonaldTrump ’s dangerous video must be taken down. I have spoken with the Sergeant-at-Arms to ensure that Capitol Police are conducting a security assessment to safeguard Rep. @Ilhan Omar, her family & her staff. They will continue to monitor & address the threats she faces. pic.twitter.com/Grb9c8S18d

Pelosi was forced to take the threats to Omar more seriously by the fact that, as the weekend wore on, more and more Democrats followed the lead of Sanders and Warren, who denounced Trump’s tweet for its incitement against the Muslim representative rather than its use of 9/11 imagery.

Trump had propelled the smear campaign against Omar into overdrive on Friday night, taking his cues from Fox News and the New York Post, which stoked outrage by distorting a reference to the attacks that Omar made during a speech in support of a Muslim civil rights group.

The raw material for the manufactured outrage was video of Omar discussing the work of the rights group, the Council on American-Islamic Relations, or CAIR, in combating anti-Muslim bigotry after the September 11 attacks. The actions of those terrorists, she told supporters of the group, had led some Americans to associate everyone of that faith with terrorism. “For far too long,” Omar said, “we have lived with the discomfort of being a second-class citizen and, frankly, I’m tired of it, and every single Muslim in this country should be tired of it. CAIR was founded after 9/11 because they recognized that some people did something and that all of us were starting to lose access to our civil liberties.”

Although Omar’s reference to the attackers having been Muslims was vague, it was not, as her enemies claimed, flip or dismissive — nor was it intended as a description of the attack itself.

The video posted on Twitter by Trump clipped out Omar’s passing reference to the attacks — set to unsettling music and played on a loop with footage of the attack in New York — and treated it as if it were proof that Omar had described the massacre as unimportant. Trump’s all-caps caption for his video, “WE WILL NEVER FORGET,” was echoed in a closing on-screen title, which read: “September 11, 2001. WE REMEMBER.”

In addition to the false accusation against Omar, that closing invocation to remember was an accidental reminder that Trump had revealed, during the 2016 campaign, that he does not, in fact, recall the events of that day clearly. By insisting, against all evidence to the contrary, that he remembered watching on television as “thousands and thousands” of American Muslims in New Jersey cheered the collapse of the towers, Trump betrayed that he was either genuinely confused and believed that something he had imagined actually took place, or that he was willing to smear an entire faith community by pretending that their behavior matched his delusion.

The gross distortion of Omar’s actual comments was initiated by a fringe Shiite Muslim cleric in Australia, Mohamad Tawhidi, whose embrace of far-right myths about Sunni Muslim plots to destroy Western civilization has made him a favorite of Australian nativists and tabloid journalists working for Rupert Murdoch. Tawhidi tweeted video of the congressperson, edited from a Daily Caller edit, along with an inflammatory lie: that “Omar mentions 9/11 and does not consider it a terrorist attack.”

That false claim, along with another lie — that Omar sought “to justify the establishment of a terrorist organization (CAIR) on US soil” — was amplified by Rep. Dan Crenshaw, a Texas Republican.