Real estate mogul and reality show host Donald Trump has officially entered the presidential race. For years, Trump has made regular media appearances (particularly on Fox News) to promote his previously-elusive presidential ambitions and push absurd conspiracies, including repeatedly questioning the validity of President Obama's birth certificate.

One of Trump's media platforms is likely in jeopardy due to his announcement -- NBC is reportedly planning to “re-evaluate Trump's role as host of 'Celebrity Apprentice' should it become necessary.”

Some of Trump's worst media commentary is below:

Trump Spent Months In 2011 Teaming Up With Fox News To Push Birther Conspiracies. In early 2011, as he was supposedly weighing his own presidential run, Trump breathed new life into the conspiracy theory that President Obama had not released a valid birth certificate and may have been hiding the fact that he was not born in America. Fox News gave Trump a platform on the network to forward his crusade and repeatedly defended him from attacks from other media outlets. After Obama embarrassed Trump by publicly releasing the long-form version of his birth certificate, several conservative media figures somehow decided the entire ordeal was a win for Trump.

Trump Suggested Obama's Long-Form Birth Certificate Was Forged. During an interview with Greta Van Susteren more than a year after the release of Obama's long-form birth certificate, Trump pointed to the “many, many people” questioning the validity of the document. (Trump had previously reportedly told conspiracy website WND that he thought the birth certificate was a forgery.) After Van Susteren pointed to the existence of a birth announcement for the president in a Hawaii newspaper, Trump claimed that report may have been planted:

A few months ago, during an appearance at the annual Conservative Political Action Conference, Trump reiterated that he is not sure whether Obama released “a real certificate.”

Trump: Obama Didn't Write His Own Memoir. Borrowing an obscure conspiracy from WND columnist Jack Cashill, Trump repeatedly claimed in 2011 and 2012 that President Obama didn't write his memoir, instead suggesting that the book was actually written by Bill Ayers.

During a 2012 appearance on Greta Van Susteren's show, Trump said, “Who really penned that book, it would be an interesting question for people to figure out ... I think somebody else had a lot to do with that book. I think he wrote the second book, which was certainly not a masterpiece. I'm very good at books, and it certainly wasn't a masterpiece.”

Trump: Climate Change Is A “Hoax” Perpetrated By Scientists “Having A Lot Of Fun.” During a rant pointing to cold winter temperatures around the country, Trump repeatedly labeled climate change a “hoax,” adding, “I think the scientists are having a lot of fun.”

As Mother Jones' Jeremy Schulman (formerly research director at Media Matters) notes, Trump has also repeatedly dismissed climate science on his Twitter account, decrying the “GLOBAL WARMING HOAX” and the “very expensive GLOBAL WARMING bullshit.”

Trump Repeatedly Linked Vaccines To Autism. Trump has frequently pushed the link between vaccines and autism despite scientific evidence to the contrary. He said on Fox News in April 2012 of vaccines: “I've seen people where they have a perfectly healthy child, and they go for the vaccinations, and a month later the child is no longer healthy.” He later tweeted, “I am being proven right about massive vaccinations--the doctors lied,” and "Healthy young child goes to doctor, gets pumped with massive shot of many vaccines, doesn't feel good and changes - AUTISM. Many such cases!