Donald Trump, the last GOP candidate standing since the beginning of May, has clinched the number of delegates necessary to become the Republican's official 2016 presidential candidate, the Associated Press reports. What pushed him over the line was a group of unbound delegates telling the AP on Thursday that they'd be backing the real estate mogul.This follows Trump making the news for telling Jimmy Kimmel on Wednesday he would be up for debating Bernie Sanders, which sounded like a serious offer, though multiple sources told CBS News that Trump was joking about going head-to-head with the guy he's dubbed "Crazy Bernie."On the Democratic side, Hillary Clinton and Sanders are both still vying for the nomination, though Clinton has an all but insurmountable lead.Trump will accept the honor as Republican nominee at the Republican convention in July.Photo via Flickr user Gage Skidmore