In response to claims that she has no chance of winning the nomination, Clinton has asserted that pledged delegates are allowed to switch sides and vote for her at the convention. Unlike Superdelegates, who are free to support either candidate, pledged delegates are supposedly promised to a specific candidate.
Well, we now know that Clinton is right. One of her pledged delegates (Jack B. Johnson of Maryland, picked in consultation with the Clinton campaign) has switched sides to Obama.
http://www.washingtonpost.com/wp-dyn/content/article/2008/05/12/AR2008051202554.html
