Although this isn’t the first time Murdoch has praised Ben Carson on social media (he tweeted that Carson was “terrific” after an appearance on The Kelly File), this tweet echoed an ongoing trend among GOP candidates and the conservative establishment: doubts about the authenticity of President Obama’s identity.The idea that Obama's not "really" something or other has dogged him since the day he took office. Just a few weeks ago, Donald Trump did nothing to correct a supporter’s suggestion that "our current president" is a Muslim — adding to a long-standing theory that doubts Obama is "really" a Christian.Trump was also a loud and early champion of another such theory: Obama is not "really" an American. The so-called birthers spent years asking for the president’s birth certificate in order for him to prove his citizenship.The message sparked outrage on Twitter, with dozens asking Murdoch to explain his remarks and some poking fun at the ridiculous notion that Murdoch thinks he can measure anyone's blackness.