"This is something Republicans have been engaged in, and one Republican in particular has been very focused on for a long time," Earnest told Stephen Colbert on Tuesday on CBS's "The Late Show."

AD

Last September, Trump acknowledged for the first time that Obama was born in the United States. But in doing so, he also claimed credit for ending the false theory that he was born elsewhere. And on more than one occasion, he sought to place the blame on Democratic rival Hillary Clinton.

AD

"You know who started the birther movement? You know who started it? Do you know who questioned his birth certificate, one of the first? Hillary Clinton. She's the one who started it. She brought it up years before it was brought up by me," Trump said in a May 2016 interview with CNN's Wolf Blitzer.

Although there's evidence that some of Clinton's supporters circulated anonymous emails questioning Obama's citizenship in 2008, when the two Democrats were vying to be the party's presidential nominee, there was no proof that Clinton herself or her campaign made such statements, according to The Washington Post's fact-checker, Michelle Ye Hee Lee.

AD

Trump started talking publicly about the birther theory in 2011, making several television appearances in which he repeatedly questioned whether Obama was actually born in Hawaii. At times, Trump referenced anonymous sources — the very action that he has denounced when criticizing negative stories about the administration.

AD

"Why doesn't he show his birth certificate? There's something on that birth certificate that he doesn't like," he said on ABC's "The View" in March 2011.

On "The Laura Ingraham Show" that same month, Trump said: "There's something on that certificate that is very bad for him. Now, somebody told me — and I have no idea if this is bad for him or not, but perhaps it would be — that where it says 'religion,' it might have 'Muslim.' And if you're a Muslim, you don't change your religion, by the way."

AD

In August 2012, more than a year after Obama released his long-form birth certificate, Trump tweeted that somebody had told him the birth certificate was a fraud.

Several Republicans also have publicly questioned Obama's citizenship — a problem that dogged Mitt Romney's presidential campaign in 2012.

Former congressman Cliff Searns (R-Fla.) did so at a town hall meeting in March 2012 and told reporters that same month that he was not convinced Obama's birth certificate was valid.

AD

Rep. Vicky Hartzler (R-Mo.) said in April 2012 that she had "a lot of doubts" about whether the birth certificate is real.

"I don't understand why he didn't show that right away. I mean, if someone asked for my birth certificate, I'd get my baby book and hand it out and say 'Here it is,'" she said, responding to a constituent's question at a town hall.

AD

Perhaps one of the more adamant believers is Arizona's Sheriff Joe Arpaio, who advocated for the theory even after Trump had abandoned it. He announced in December that a five-year investigation had found that Obama's birth certificate was, in fact, forged. In a presentation in front of journalists, he and a member of his Sheriff's Office's Cold Case Posse highlighted what they called "9 points of forgery" on the document, the Arizona Republic reported.

AD

On the "Late Show," Earnest, who was the White House press secretary from 2014 until Obama left office, said Republicans have sought to delegitimize Obama for the last eight years by spreading the fake news that he wasn't born in the United States. Trump has repeatedly used the term "fake news" to describe several negative stories about his administration.

Many Republicans, however, have distanced themselves from the birther theory.

In 2011, for instance, Arizona's then-governor, Jan Brewer, vetoed the so-called "birther bill" that would have required presidential candidates to provide documentation proving they were born in the United States to get on the state ballot.

AD

Last September, Trump's running mate, Mike Pence, told reporters that he believed Obama was born in Hawaii, even as Trump at that time avoided renouncing the theory. Former GOP presidential candidate Ben Carson told CNN's Jake Tapper then that it would be a "good idea" for Trump to apologize for pushing the birther theory.

AD

Earnest also spoke briefly about his counterpart in the White House, Sean Spicer, and the Trump administration's relationship with the press.

"There's supposed to be friction and tension between the White House press corps and the White House," Earnest said. "The day that there is no friction and tension between the White House press corps and the White House is the day that the press corps has stopped doing their job."

Asked about Spicer's first news conference in January, when he read a prepared speech berating the press for reporting on the size of Trump's inauguration crowd, Earnest said it was "a strange way to start." Spicer falsely claimed that Trump's crowd size was the largest ever for an inauguration.

AD

"One of the things you have to recognize about being the White House press secretary is, your job is to go out there every single — it's a job not unlike yours, you have to go out there every single day and speak to the press corps on live television," Earnest said. "You have to keep that in mind. And so spending all the credibility he spent on the very first day I think was a little short-sighted."

AD

Earnest also said it's "entirely fair" for media organizations to criticize the White House for excluding news organizations, notably CNN, the New York Times, Politico and others, from an off-camera press briefing. Spicer denied doing so in an interview on Fox News Insider, saying the pool of media members rotates every day and the said news organizations were not part of the pool.

"I think any assertion that they were banned or whatever is completely ridiculous," Spicer said.