One of the oddest features of the 2016 presidential race is that the Republican nominee, Donald Trump, emerged on the political scene this decade by repeatedly questioning whether President Barack Obama was born in America — and yet it seems Trump’s embrace of this crackpot conspiracy theory has hardly been discussed during this campaign.

Yes, the GOP nominee was the highest-profile "birther" for much of 2011, and continued to perpetuate the movement’s debunked nonsense for many years afterward, despite it being fringe racist nonsense.

Now, though, the Washington Post’s Robert Costa has elevated the subject again. In an interview with Trump on Wednesday, Costa asked the candidate whether he now believed Obama was born in Hawaii, and Trump refused to answer. "I’ll answer that question at the right time," Trump told Costa. "I just don’t want to answer it yet."

And when Costa followed up by pointing out that Trump’s top adviser, Kellyanne Conway, has said that Trump now believed Obama was born in the US, Trump was noncommittal. "It’s okay. She’s allowed to speak what she thinks," Trump told Costa. "I want to focus on jobs. I want to focus on other things."

Hours after Costa’s story was posted on Thursday, Trump adviser Jason Miller sent out a statement claiming that "Mr. Trump believes that President Obama was born in the United States." Furthermore, Miller ludicrously tried to give Trump credit for bringing "this ugly incident to its conclusion by successfully compelling President Obama to release his birth certificate," as if he were doing some sort of public service.

Finally, on Friday, Trump himself begrudgingly gave an extremely brief statement that "President Barack Obama was born in the United States, period," and again dishonestly blamed Clinton for supposedly starting the controversy. But he shouldn’t be allowed to worm out of this so easily, because birtherism is in many ways the urtext of Trump’s presidential campaign. It demonstrates his willingness to mainstream fringe racism, his desire to flout the norms of political discourse, his ability to play the media, and his imperviousness to facts. And Trump has never truly been held to account for it during this campaign.

What is birtherism?

The US Constitution requires that the president of the United States be a "natural born citizen." Obama is one, by virtue of having been born in Hawaii (to a US citizen mother). But birthers raised the question ... what if he wasn’t?

When Obama first ran for president in 2008, he had a very different background from all previous presidential nominees. He wasn’t white, his middle name was Hussein, and he had lived abroad for several years as a child. And the fever swamps of the internet responded to this by letting their imaginations run wild. One fringe theory was that Obama was a "secret Muslim." Another was that he was lying about having been born in Hawaii, and was in fact born in another country — likely Kenya — and was therefore ineligible for the presidency.

This chatter first emerged during the contentious 2008 Democratic primary, but was limited to chain emails and such rather than being associated with anyone prominent, according to Politico. It then continued during the general election and Obama’s presidency and was embraced by little-known fringe figures like Orly Taitz and Philip Berg, and the right-wing pundit Jerome Corsi.

It never made a lick of sense. In the summer of 2008, the Obama campaign released his shortform birth certificate from the Hawaii Department of Health. Fact-checkers examined it and were satisfied that it was authentic. Furthermore, there were contemporaneous announcements of Obama’s birth printed in Hawaiian newspapers at the time. Then in 2011, Obama finally dredged up his longform birth certificate. But since conspiracy theorists are conspiracy theorists, they invented all sorts of reasons to dismiss and disbelieve all this evidence.

What was Trump’s role in the birther movement?

As Trump publicly considered a presidential campaign against Obama in 2011, he gained media attention and popularity on the right by becoming the highest-profile "birther" ever. Here’s the timeline:

February 10, 2011: Trump gives a speech to CPAC in which he says he’s thinking about running for president, and dips his toe into birtherism. "Our current president came out of nowhere. Came out of nowhere," he told the crowd. "In fact, I'll go a step further: The people that went to school with him, they never saw him, they don't know who he is. It's crazy."

March 23, 2011: Trump says on The View : "I want him to show his birth certificate. I want him to show his birth certificate. ... There's something on that birth certificate that he doesn't like."

: "I want him to show his birth certificate. I want him to show his birth certificate. ... There's something on that birth certificate that he doesn't like." March 28, 2011: Asked on Fox & Friends whether he thinks Obama was born in this country, Trump responds, "I am really concerned." He went on to speculate that the birth announcement for Obama in a Hawaii newspaper could have been planted "for whatever reason."

whether he thinks Obama was born in this country, Trump responds, "I am really concerned." He went on to speculate that the birth announcement for Obama in a Hawaii newspaper could have been planted "for whatever reason." March 30, 2011: Trump says on The O’Reilly Factor , "If you are going to be president of the United States you have to be born in this country. And there is a doubt as to whether or not he was. ... He doesn't have a birth certificate. He may have one, but there's something on that, maybe religion, maybe it says he is a Muslim. I don't know. Maybe he doesn't want that. Or he may not have one. But I will tell you this. If he wasn't born in this country, it's one of the great scams of all time."

, "If you are going to be president of the United States you have to be born in this country. And there is a doubt as to whether or not he was. ... He doesn't have a birth certificate. He may have one, but there's something on that, maybe religion, maybe it says he is a Muslim. I don't know. Maybe he doesn't want that. Or he may not have one. But I will tell you this. If he wasn't born in this country, it's one of the great scams of all time." April 7, 2011: Trump claims on NBC that he has sent a team of investigators to Hawaii to study the matter. "I have people that have been studying it, and they cannot believe what they're finding," he said. "You are not allowed to be a president if you're not born in this country. Right now I have real doubts."

April 15, 2011: A poll shows Trump in first place in the Republican primary race (though he hasn’t announced a candidacy and won’t end up doing so).

April 19, 2011: In a statement that is hilarious in retrospect, Trump tells ABC he would "love" to release his tax returns, and that he’d "maybe" do it once Obama released his birth certificate. (More than five years later, Trump has still never released his tax returns.)

April 25, 2011: Trump tells Anderson Cooper, "I've been told very recently, Anderson, that the birth certificate is missing. I've been told that it's not there or it doesn't exist. And if that's the case, it's a big problem."

April 27, 2011: President Obama releases his original longform birth certificate, attempting to at long last put the matter to rest. Trump responds by ... simply changing the subject to Obama’s college records. "The word is, according to what I’ve read, that he was a terrible student when he went to Occidental. He then gets to Columbia; he then gets to Harvard," Trump said. "Maybe that’s right, or maybe it’s wrong. But I don’t know why he doesn’t release his records."

Okay, but after Obama delivered his birth certificate, Trump moved on, right?

Who are you kidding? It's very hard to convince conspiracy theorists that they're wrong with evidence, because they will just invent new reasons to disbelieve any piece of evidence they don't like. Plus, this is Donald Trump we’re talking about.

So contrary to his campaign’s transparently false statement that Trump brought "closure to the issue" in 2011, Trump continued to spread nonsense about it for years afterward and come up with new bogus reasons not to believe the document Obama released:

Let's take a closer look at that birth certificate. @BarackObama was described in 2003 as being "born in Kenya." http://t.co/vfqJesJL — Donald J. Trump (@realDonaldTrump) May 18, 2012

An 'extremely credible source' has called my office and told me that @BarackObama's birth certificate is a fraud. — Donald J. Trump (@realDonaldTrump) August 6, 2012

Why do the Republicans keep apologizing on the so called "birther" issue? No more apologies--take the offensive! — Donald J. Trump (@realDonaldTrump) August 27, 2012

Wake Up America! See article: "Israeli Science: Obama Birth Certificate is a Fake" http://t.co/f7esUdSz — Donald J. Trump (@realDonaldTrump) September 13, 2012

How amazing, the State Health Director who verified copies of Obama’s "birth certificate" died in plane crash today. All others lived — Donald J. Trump (@realDonaldTrump) December 12, 2013

Attention all hackers: You are hacking everything else so please hack Obama's college records (destroyed?) and check "place of birth" — Donald J. Trump (@realDonaldTrump) September 6, 2014

But other than all that, there was closure!

Wait, though — Trump has repeatedly blamed Hillary Clinton for starting the birther movement. He wouldn’t lie to me about this, would he?

Just remember, the birther movement was started by Hillary Clinton in 2008. She was all in! — Donald J. Trump (@realDonaldTrump) September 23, 2015

There’s no evidence that Hillary Clinton or her 2008 campaign had anything to do with the birther theory — none. Nonpartisan fact-checkers have repeatedly debunked this claim, as you can see at PolitiFact, FactCheck, CNN, and the Washington Post.

Now, the small grain of truth here is that a few Clinton supporters did circulate the theory online during the contentious 2008 primary, according to Politico’s Ben Smith — though it's not really clear that they were the first to do so (as Smith claims), since there was contemporaneous chatter about this in right-wing circles online at the time too. But once the primary concluded and Obama first released his birth certificate that summer, this chatter quieted down in Democratic circles, and moved instead to more conspiracy-focused and right-wing precincts.

Update: This piece was updated with Trump's statement on Friday, and some new links on the origins of the birther controversy in 2008.

Watch: Trump on his role in the birther movement