Not even Oprah Winfrey could get Sen. Barack Obama to declare his presidential ambitions during his Oct. 18 appearance on her talk show. But thanks to George Clooney, OK! can exclusively reveal that the junior senator from Illinois IS going to take on all challengers for the Democratic nomination in 2008. ‘I just spoke with Barack and he is going to run,’ a beaming George told OK! at a celebration for Tony Bennett’s 80th birthday in Hollywood. ‘I just hung up the phone with him.’ Will George endorse and campaign for Obama? George’s answer was a big thumbs-up! The Hawaiian-born Obama, 45, married and father of two, has been a senator only since January, 2005, but has already won the hearts of many in Hollywood, including Oprah, who has long been encouraging him to run.