Andy Burnham is on course for a coronation as Labour’s new leader as the only declared candidate ahead of nominations for the contest opening on Thursday.Al Carns, thought to be the final remaining potential challenger to the former Greater Manchester mayor, ruled himself out of the running on Wednesday evening.Former armed forces minister Mr Carns said: “I’d hoped a leadership contest would give us the opportunity for a proper debate.“But months of internal Labour politics isn’t what the country needs right now. We’ve got to get on with the job.“Andy Burnham’s earned this and he’s got my full backing.”Prime Minister Sir Keir Starmer resigned last month (PA)PA WireProspective candidates need the backing of 81 MPs to put themselves forward to replace Sir Keir Starmer, who resigned last mont