A former professor of Barack Obama has turned against his one-time student and publicly urged voters not to re-elect him. Roberto Unger posted a video on YouTube detailing the reasons why he believes the President does not deserve a second term in the White House. Mr Unger, a prominent Brazilian politician and an adviser to Obama in 2008, said: 'President Obama must be defeated in the coming election. He has failed to advance the progressive cause in the United States.'