Mr. Trump initially resisted taping the video, agreeing to do it only after aides pressed him and he appeared to suddenly realize he could face legal risk for prodding the mob, coming shortly after the chief federal prosecutor for Washington left open the possibility of investigating the president for illegally inciting the attack by telling supporters to march on the Capitol and show strength…

“We are looking at all actors, not only the people who went into the building,” Michael R. Sherwin, the U.S. attorney in Washington, told reporters. Asked if that included Mr. Trump, he did not rule it out. “We’re looking at all actors,” he repeated. “If the evidence fits the elements of a crime, they’re going to be charged.”…

In the weeks since the election, Mr. Trump has shrunk his circle, shutting out those who told him to concede and favoring those telling him what he wanted to hear, that he was somehow cheated of the presidency. As supporters stormed into the Capitol on Wednesday, Mr. Trump was initially pleased, officials said, and disregarded aides pleading with him to intercede.