reporter: never was that more stark than on april 30, 2011, at the white house correspondent s dinner, president obama was relentless in roasting trump. but no one is happier, no one is prouder to put this birth certificate matter to rest than the donald. and that s because he can finally get back to focusing on the issues that matter, like did we fake the moon landing? what really happened in roswell? and where are biggie and tupac? reporter: the audience roared. trump seethed. for trump, this was a decisive moment. this was the exact moment when i think he decided, i m going to run for president and i m going to beat that guy. reporter: in the ensuing years, trump would invoke the laughing stock strategy when slamming obama in tweets, and it has since become a political