Democratic presidential candidates over the weekend turned their guns on billionaire former New York mayor Michael Bloomberg as he rises swiftly in the polls. Three separate surveys put Mr Bloomberg, who is estimated to have spent $386 million (£296 million) on his campaign, in third place. But just as he starts to make his presence felt in the race allegations of past sexism and controversy over his stop-and-frisk policy in New York have provided ammunition for his opponents. Mr Bloomberg has had to explain the policy he enacted while New York mayor, which critics said disproportionately affected black and Latino men. Mr Bloomberg, who is garnering considerable African-American support, has apologised for the strategy. But this did not stop his rivals capitalising on the issue as they did the round of political talk shows....