ADDIS ABABA, Ethiopia (AP) — President Barack Obama unleashed a blistering and belittling rebuke of Republican White House hopefuls Monday, calling their attack on his landmark nuclear deal with Iran "ridiculous if it weren't so sad." Standing before television cameras during a trip to Africa, Obama suggested the bellicose rhetoric from some GOP candidates was an attempt to divert attention from Donald Trump, the wealthy businessman-turned presidential contender whose popularity is confounding the Republican field.