The "alt-right," which is shorthand for the "alternative right," is composed of many far-right ideologies.
One of the best-known members of the alt-right is Jared Taylor, the editor of American Renaissance, which he has described as a white advocacy organization.
"We weren’t counting on Hillary for being so generous in sharing the spotlight with us," he said, referring to Clinton's speech on the alt-right this afternoon.
Taylor identifies as being a member of the alt-right and described it as "a dissident movement" where "the prevailing orthodoxy about race is that it is an insignificant phenomenon."
"It's quite clear to us that the races are not equivalent and interchangeable," he said, arguing that if you were to take a majority white country and "replace it with Syrians and Zulus and Guatemalans and Cambodians, you wouldn’t have the same country."
But Mark Potok, a senior fellow at the SPLC, describes the labels as fitting, saying that American Renaissance is "a racist journal."
"They're sort of more presentable white supremacists," Potok said of members of the alt-right, describing them as a "fairly suit-and-tie bunch."
"They're not skinheads.... They don't use ethnic slurs," he added.
Potok told ABC News that the prevailing ideology of the alt-right "has informed the extreme right" and focuses on "that it is not black people or other minorities who are oppressed but in fact white people are."
"They see whites as a beleaguered race whose civilization is being destroyed as we speak," he said.
The intersection between the alt-right and the 2016 race largely centers around Trump's campaign. Taylor told ABC News that he plans to vote for Trump and said he hopes he wins, though he has not had any formal contact with Trump's campaign.
Kellyanne Conway, Trump's recently appointed campaign manager, said today that she is "not that familiar with" the alt-right and denied that it was factoring into the campaign's tactics and platforms.
"We’ve never even discussed it internally. It certainly isn’t part of our strategy meetings, it’s nothing that Mr. Trump says out on stump," Conway told CBS this morning.
"Through the course of this campaign, we have seen him go from being the original birther questioning the legitimacy of President Obama as our first African-American president to openly courting the support of white nationalists, and now in appointing Steve Bannon from Breitbart to be the head of his campaign," Fallon said.
Trump has repeatedly denied courting the support of white supremacists, telling CBS News earlier this year, "I don't like any group of hate. Hate groups are not for me.”
Milo Yiannopoulos, a conservative figure who made headlines earlier this summer when he was banned from Twitter after the trolling attacks on actress Leslie Jones, is widely considered to be one of the best-known figures who identifies with the alt-right movement.
"There are many things that separate the alternative right from old-school racist skinheads (to whom they are often idiotically compared), but one thing stands out above all else: intelligence. Skinheads, by and large, are low-information, low-IQ thugs driven by the thrill of violence and tribal hatred. The alternative right are a much smarter group of people -- which perhaps suggests why the Left hates them so much. They’re dangerously bright," Yiannopoulos and fellow Breitbart writer Allum Bokhari wrote in a March column.
Taylor admitted that it's "absolutely impossible to say" how large the movement is, but said "it is growing very rapidly, no question about that."
"I would say that there are millions of Americans who subscribe to the alt-right philosophies. But the vast majority of them can't afford to be public," Taylor said. "Despite all of this nonsense that we are a tolerant society, there are certain views on which it [American society] is absolutely intolerant of diversity."
ABC News political analyst Matthew Dowd said that while the alt-right is gaining an audience in this presidential race, some of the ideas and sentiments its supporters stand behind have been part of American politics for quite some time.
"This isn't new in our history," he said. "Some of them were [Ross] Perot voters in 1992 who were mad about trade deals and frustrated at D.C. And ironically it is George Wallace's birthday today, who also appealed to this group."
He added: "This is a group of voters has risen as a powerful voting bloc in the GOP. So in years past, this group of working class voters were with Democrats, and now they are with Trump and the GOP."