Hillary Clinton has joked about it, called it partisan and blamed it on turf wars between federal agencies, but questions about her use of private email as Secretary of State are not going away. Some intelligence officials say some messages should have been classified – two of them as Top Secret. The FBI is investigating a possible crime, and polls show serious damage to her credibility with the voters. Has Clinton’s damage-control effort backfired? Is the controversy creating an opening for Joe Biden to launch a campaign for the Democratic presidential nomination?