"People want to talk to me," Spencer told NBC News from outside the Gaylord National Harbor complex. "They don't want to talk to these boring conservatives. They want to learn about ideas whose time has come, not whose time has passed."
Spencer, who has frequently attended CPAC without incident, became a minor media sensation during and after the 2016 election. But one of the first speeches at this year's conference challenged the media to stop referring to the alt-right as conservative.
"There is a sinister organization that is trying to worm its way into our ranks," said Dan Schneider, the executive director of the American Conservative Union, which runs CPAC. "We must not be deceived by [a] hateful, left-wing fascist group."
There was an irony to Spencer's expulsion on the same day the conference featured White House strategist Stephen Bannon, the former CEO of Breitbart News, who once called the site "the platform for the alt-right."
In 2013 and 2014, Breitbart News sponsored forums on the outskirts of CPAC called "The Uninvited," featuring guests who were not welcome on the main stage due to controversial views on Islam and immigration.
"I didn't like 'the Uninvited,'" said the ACU's president, Matt Schlapp, introducing Bannon with White House Chief of Staff Reince Preibus. "Everybody's a part of our conservative family."
But not Spencer, apparently. Over seven tense, perplexing minutes, Schneider argued that the alt-right was philosophically left-wing because it departed from a conservatism in which "the individual" was sovereign.
"They hate the Constitution. They hate free markets. They hate pluralism," Schneider said. "Fascists tend to want big government control."
The argument wasn't unique to Schneider. In 2009's "Liberal Fascism," the columnist Jonah Goldberg, whose work appears on JWR, drew a zigging line from the fascism of the 1930s to the welfare state liberalism of the Clinton/Obama era.
But inside the main ballroom of CPAC, the argument didn't generate much applause. Some in the audience cheered the denunciation of "left-wing fascism," while a few listeners walked out.
Among the walkouts was Spencer, who was quickly recognized by reporters and attracted such a large crowd of them that security staff asked him to move away from the entrance, which was rapidly being blocked. Their questions ranged from Spencer's reaction to the denunciation, to whether he supported the Ku Klux Klan, to whether black Americans deserved credit for creating rock 'n' roll.
"Depeche Mode is the official band of the alt-right," said Spencer - a comment that would be denounced by the British synth-rock band by the end of the day.
Inside the Gaylord, more and more cameras and recorders were shoved toward Spencer as he reminded reporters that the self-appointed guardians of conservatism had waited to trust Trump long after the alt-right had.
"'Donald Trump isn't a conservative' - that's what they were saying a year ago," said Spencer.
As the throng of reporters moved, Spencer was stopped by JP Sheehan, a CPAC attendee wearing a black-and-gold Make America Great Again baseball cap.
"Praise kek!" said Sheehan, posing for a selfie with Spencer and repeating a meme that had been adopted by the alt-right. "He's the coolest guy."
The growing crowd attracted more nervous attention from security, and after a few more minutes, they arrived to expel Spencer.
"I'm not welcome on the property?" Spencer asked.
"I'm not going to debate this," said the guard. "This is private property. They want you off the property."
After Spencer asked if he could stay if he would simply "stay out of trouble," he said a hashtag - "Free Spencer" - into the cameras, and posed for another photo as he was taken outside.
Spencer, who became somewhat infamous after leading a cry of "hail Trump, hail victory, hail our people" at an NPI conference, was gone.