Republican presidential nominee Donald Trump has caused an uproar by repeatedly associating President Barack Obama with terrorism, raising questions about his citizenship and casting aspersions on his loyalty to the country — but what is often lost in all the outrage is the fact that the real estate mogul's views are not that far outside the mainstream of conservative opinion.

While Trump has differentiated himself as the first presidential candidate to lend credence to conspiracy theories about Obama's motives and background, his views are shared by a majority of Republican voters and have been for some time.

A recent NBC News Survey Monkey poll found that a whopping 72 percent of Republicans have doubts about Obama's citizenship and 41 percent are emphatic that he was foreign born. Meanwhile, 31 percent are unsure if he is an American, leaving 27 percent who acknowledge that their country's president was born in the U.S.

The fact that most rank-and-file Republicans refuse to accept the legitimacy of Obama's birth certificate has long been something of an embarrassing open secret which prominent party leaders have chosen to sidestep. The reality is that even after the president begrudgingly released his long-form birth certificate — confirming that was born in Hawaii — to the public in April of 2011 to quash the rumors, it did little to shake conservatives' steadfast belief that he is a fraud.

Prior to the press conference where Obama unveiled the document, a Gallup poll found that 43 percent of Republicans definitely or probably believed he was born in another country. The number dropped dramatically to 23 percent following his revelation, but by the following year, the number had already risen back to 37 percent. Meanwhile, a Gallup poll that same year found that a majority of Republicans either believed the president was a Muslim or were unsure if he was one.

Related: Trump Calls Obama the 'Founder of ISIS' Over Anti-Terror Strategy

In 2013, a Farleigh Dickinson University study determined that 64 percent of Republicans believed that the president was "probably" hiding important information about his past. And by last year, the number of Republicans who thought the president — who has publicly long identified as a Christian — is a Muslim actually rose to a higher level than those that did in 2010.

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This phenomenon of cognitive dissonance was described in part by the late media critic Danny Schechter in a 2011 Consortium column as a triumph of "feelings over facts."

Some of the fervor behind these unsubstantiated beliefs could be attributed to the partisan tone of general election campaigns, both in 2008, 2012 and today. But there is also little doubt that the stoking of the birther conspiracy by prominent conservative leaders has helped keep the premise alive, and even perhaps codified it as a tenet of conservative orthodoxy.

Although birtherism periodically has cropped up in conservative state legislatures (who have passed birth certificate requirements for candidates, in an obvious nod to the conspiracy) and has been given voice by some far right politicos like former Rep. Michele Bachmann, it has always been swept under the rug — until a certain former reality star seized the national spotlight.

Trump has for years now been the most prominent booster of "birtherism," although he now claims he doesn't speak about the topic anymore — even though he really wants to. Instead, he has trafficked in racially insensitive dog whistles (like making a point of emphasizing the president's middle name) and attempted to conflate Obama with terrorism (most recently, calling him the "MVP" of ISIS).

By championing birtherism, Trump arguably launched his political career, but as he is keen to point out — he is not the originator of the concept.

Contrary to Trump's claims that it was Hillary Clinton, that individual is widely believed to be Andy Martin, a fringe Illinois-based figure who has run unsuccessfully for office as both a Democrat and Republican for several decades. Martin circulated a story alleging Obama was a Muslim following the then-U.S. Senate candidate's breakthrough performance at the 2004 Democratic Convention.

Related: 'Birtherism' Is Back and That May Be Bad News For Trump

Due to Obama's childhood stints living abroad and African heritage (his father was born in Kenya), the insinuations picked up steam, but did little to derail his Senate candidacy. And while the rumors didn't die down during his first bid for the presidency in 2008, they were almost always dismissed by his political foes. The most famous example of which was Republican presidential nominee Sen. John McCain's decision to rebuff a supporter who called Obama a Muslim during one of his campaign appearances.

Today, even if Trump no longer explicitly makes the claim that Obama is not an American citizen, the theory has taken on a life of its own. For every article insisting their is no evidence of the president's religion or place of birth being anything different than he says it is, there are skeptics who point to a phantom birth certificate from Kenya showing he was born in a Mombasa, claim he was "raised Muslim," or insist he was educated in a radical Islamic school as child while briefly living in Indonesia.

If one were to take the logic of the birther claims to their logical conclusion, they would have to not just believe that the president is illegitimate, but also accept that Obama's political ascent and personal narrative has been a decades-long plot, involving countless co-conspirators, all with the dubious aim of putting an ostensibly anti-American man in the White House.

Ironically, Martin, who once alleged that Obama was trained to "overthrow the government," stopped claiming that the president was foreign born back in 2008. Eight years ago he told CNN that after conducting his own personal investigation, he concluded that the president's father was not Barack Obama Sr. but instead black poet and activist Frank Marshall Davis, who was accused of having Communist ties during the McCarthy witch-hunt era.

Related: Sanders Takes on Donald Trump's Role in 'Birther' Movement

Obama wrote about Davis (referred to only as "Frank") in this best-selling 1995 autobiography "Dreams From My Father," describing him affectionately, but also somewhat dismissively, as a radical stuck in a "sixties time warp." According to Obama, Davis, who would have been in his 50s at the time of his birth, was a friend of his grandfather's — but that hasn't prevented a widely discredited 2012 documentary, entitled "Dreams From My Real Father," from alleging that not only that Obama's late mother was involved in fetish pornography, but that she also engaged in a torrid love affair with Davis.

“My election was not a sudden political phenomenon,” a narrator posing as Obama says in the film. “It was the culmination of an American socialist movement that my real father, Frank Marshall Davis, nurtured in Chicago and Hawaii, and has been quietly infiltrating the U.S. economy, universities, and media for decades.”

While most Republican elected officials would almost certainly disavow this kind of propaganda, millions of copies of it were reportedly shipped to conservative voters in swing states during the fall of 2012. According to the Daily Beast, the "film" was screened during a right-wing themed film festival during the Republican National Convention that year in Tampa.

The then-chairman of the Alabama Republican Party, Bill Armistead, even recommended it to his constituents, while also promoting an anti-Obama documentary (inspired by a book that delved into the president's deceased mother's sex life) by controversial conservative filmmaker Dinesh D'Souza.

"I’m going to tell you about another movie. The name of it is ‘Dreams From My Real Father.’ That is absolutely frightening," he told an audience of Republican women in Fairhope, Alabama. "I’ve seen it. I verified that it is factual, all of it. People can determine.”

Despite a few unflattering headlines about having "gone birther," Armistead didn't lose his job or get reprimanded publicly by the GOP. In fact, he was re-elected to the state party chairmanship over a very highly touted opponent the following year and served two more, stepping down last February with little fanfare.