WASHINGTON — By the time Richard B. Spencer, the leading ideologue of the alt-right movement and the final speaker of the night, rose to address a gathering of his followers on Saturday, the crowd was restless.

In 11 hours of speeches and panel discussions in a federal building named after Ronald Reagan a few blocks from the White House, a succession of speakers had laid out a harsh vision for the future, but had denounced violence and said that Hispanic citizens and black Americans had nothing to fear. Earlier in the day, Mr. Spencer himself had urged the group to start acting less like an underground organization and more like the establishment.

But now his tone changed as he began to tell the audience of more than 200 people, mostly young men, what they had been waiting to hear. He railed against Jews and, with a smile, quoted Nazi propaganda in the original German. America, he said, belonged to white people, whom he called the “children of the sun,” a race of conquerors and creators who had been marginalized but now, in the era of President-elect Donald J. Trump, were “awakening to their own identity.”

As he finished, several audience members had their arms outstretched in a Nazi salute. Mr. Spencer called out: “Hail Trump! Hail our people!” and then, “Hail victory!” — the English translation of the Nazi exhortation “Sieg Heil!” The room shouted back.