Mr. Trump already tried to recalibrate by ripping up his speech at the Kennedy Space Center on Saturday after the launch of the new crewed SpaceX rocket and adding a long passage about Mr. Floyd. In the speech, Mr. Trump repeated his calls for law and order, but in more measured terms and leavened by expressions of sympathy for Mr. Floyd’s family, whom he had called to offer condolences.
Aides were disappointed that the remarks, delivered late Saturday afternoon as part of a speech otherwise celebrating the triumph of the space program, did not get wider attention, but they said they hoped they would break through. Several administration officials said Mr. Trump was genuinely horrified by the video of Mr. Floyd’s last minutes, mentioning it several times in private conversations over the last few days.
Mr. Trump and his team seemed taken off guard by the protests that materialized outside the White House on Friday night. Hundreds of people surged toward the White House as Secret Service and United States Park Police officers sought to block them. Bricks and bottles were thrown, and the police responded with pepper spray. At one point, an official said, a barricade near the Treasury Department next door to the White House was penetrated.
It was not clear what specifically prompted the Secret Service to whisk Mr. Trump to the Presidential Emergency Operations Center, as the underground bunker is known, but the agency has protocols for protecting the president when the building is threatened. Vice President Dick Cheney was brought to the bunker on Sept. 11, 2001, when the authorities feared one of the planes hijacked by Al Qaeda was heading toward the White House. President George W. Bush, who was out of town until that evening, was rushed there later after a false alarm of another plane threat.
The bunker has not been used much, if at all, since those early days of the war on terrorism, but it has been hardened to withstand the force of a passenger jet crashing into the mansion above. The president and his family were rattled by their experience on Friday night, according to several advisers.
After his evening in the bunker, Mr. Trump emerged on Saturday morning to boast that he never felt unsafe and vow to sic “vicious dogs” and “ominous weapons” on intruders. Melania Trump, anxious about the protests, opted at the last minute not to travel to Florida for the rocket launch on Saturday.
After Mr. Trump returned to the White House from Florida on Saturday, he found a White House again under siege. This time, security was ready. Washington police blocked off roads for blocks around the building, while hundreds of police officers and National Guard troops ringed the exterior perimeter wearing helmets and riot gear and holding up plastic shields.