I reposted the link which had expired. Sorry.
My husband writes books and articles on the American presidency among other subjects. He doesn't like me to talk about him here (except maybe his garden), but he'll be interviewed on BBC World Radio today about the vice-presidency in American politics. It will be on several times, but here's the link for anyone who likes to listen to political analysis. This is his most recent book. http://www.bbc.co.uk/worldservice/programmes/analysis.shtml