Addis Ababa, Ethiopia - President Barack Obama delivered a withering critique of the vitriol-filled 2016 US presidential debate on Monday, saying its tone was not worthy of voters.With 18 months left at the White House, Obama hit out at "outrageous" attention-grabbing attacks, which he said "have become all too commonplace" in America's acerbic and highly polarised politics."We are creating a culture that is not conducive to good policy or good politics," Obama said. "The American people deserve better," Obama said.He zeroed in on Republican presidential candidates Donald Trump and Mike Huckabee. Speaking in Ethiopia, Obama berated Huckabee for his suggestion that a nuclear deal with Iran would march Israelis to the "door of the oven".He described that as part of a "general pattern" that would be "considered ridiculous if it weren't so sad".Obama is lobbying hard for the Iran deal, which is seen by aides as a signature achievement of his presidency.The deal would place curbs on Iran's nuclear programme in exchange for relief from US and international sanctions, ending more than a decade of tensions.But Republicans have resoundingly rejected the agreement - saying Iran should completely dismantle its nuclear programme - and made it a central topic in the election campaign.Obama also took issue with Trump's "outrageous" comments criticising the war record of Republican Senator John McCain, who was a prisoner of war in Vietnam.Obama said that McCain, who he beat in 2008 to become president, was "somebody who endured torture and conducted himself with exemplary patriotism."Trump's brash rhetoric has made him a gadfly with the Republican party establishment, but it has also earned him frequent and prominent television spots on celebrity obsessed US news channels.Despite the disapproval of party heavyweights, the trash-talking billionaire is polling well with voters angry with Republican party leadership.A poll released on Sunday showed him with a big lead in New Hampshire, a key early primary state."These are leaders of the Republican party," Obama said."It's not the kind of leadership that is needed for America right now and I don't think that's what anybody, Democrat, Republican or independent is looking for."Obama has long been irked by sharp edged Republican rhetoric, which has cast him as foreigner born in Kenya, and more recently, a state sponsor of terror.But on a landmark visit to Africa, he perhaps has a glimmer of a political opportunity to turn the tables."Presidential debates deserve better," he said. "In 18 months, I'm turning over the keys. I want to make sure I'm turning over the keys to somebody who's serious about the serious problems the country faces and the world faces."