Michael Bloomberg, the mayor of New York, introduced Barack Obama this morning at a speech in New York sparking off a whole slew of rumours about an Obama-Bloomberg ticket. Certainly Bloomberg--a Democrat turned Republican turned independent--reinforces Obama’s post-partisan message. While his executive experience would reassure voters who worry that Obama hasn’t run anything apart from the Harvard Law Review in his life. Working against that is that it is hard to see any states that Bloomberg puts in play while his views on gun control could cause problems for the ticket.