From physicsworld.com, May 2, 2008

Organizers of ScienceDebate 2008 are "disappointed" but "not surprised" that the three main US presidential candidates have ignored invitations to participate in a public debate on science that was scheduled to take place today. Friday 2 May was one of three possible dates this month that had been put forward to the candidates after the original date - 18 April - had to be cancelled, also because of a poor response.

Read more here:

http://physicsworld.com/cws/article/news/34071