Donald Trump is closer than ever to capturing the Republican presidential nomination. Voters will be heading to the polls in key states, including Florida, Ohio and Missouri, on Mega Tuesday, and when it's all said and done, Trump could emerge atop the once crowded GOP field of contenders.

It's a frightening prospect for Americans who are appalled by his bigoted rhetoric and the violence he's egged on at his campaign rallies. But, as Slate's Jamelle Bouie presciently wrote in an article published Sunday, Trump's rise represents a rebuke of Barack Obama's presidency — and a return to white majority politics.

"Not only does he lead a movement of almost exclusively disaffected whites," Bouie wrote, "but he wins his strongest support in states and counties with the greatest amounts of racial polarization."

That said, Trump is no newcomer. He's been floating around the fringes of presidential politics for nearly 30 years. And he's been spouting the same racist, anti-immigrant rhetoric all that time. When he ran for president four years ago, plenty of big names blasted his racist, anti-immigrant rhetoric. Here are a few:

Jon Stewart

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The former Daily Show host took Trump to task after he started the whole birther fiasco, pointing out in 2011 that even Michele Bachman and Bill O'Reilly had even come to Obama's defense. "Today's tale of principle behavior," Stewart said on the show, "starts with professional meglomaniac Donald Trump." Watch the video here.

Whoopi Goldberg

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Trump's birther claims smacked of "dog-whistled racism," the New York Daily News wrote in 2011. "I'm getting tired of trying to find reasons not to think of stuff as being racist," Goldberg told the newspaper about Trump's defense against charges of racism at the time. "Being black, when you say, 'You know, this is racist,' 9,000 people say, 'Oh, no, you're just playing the race card.' Well, you know what? I'm playing the damn card now."

Allen Roskoff, gay activist

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Roskoff has spent decades protesting injustices to LGBT communities, but he leveled some of his most pointed criticism at Trump in 2011. "He's an extreme bigot," Roskoff told the Daily News. "Not only should gays be furious, we should be boycotting the products of the advertisers on his TV show and certainly boycotting his casinos and hotels and apartment buildings."

David Letterman

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The former Late Show host didn't hold back in 2011 when Dr. Phil asked what he thought of Trump. Letterman said Trump's birther comments "smack of racism."

"Nobody should be amused by that tactic," Letterman said.

Michael Eric Dyson, African-American scholar

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Dyson has been a close observer of Obama's presidency, and wrote early on about the racist opposition to his time in office. When Trump first began floating his birther conspiracies about Obama, Dyson, on the Sunday talk show Face the Nation in 2011, called it "racism by inference."

"Skepticism about black intelligence and suspicion about black humanity have gone hand in hand throughout the history of this country in feeding the perception that black people don't quite measure up," he said.

Another election year, another run for Trump. But this time, everyone is listening.

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