At this stage in the presidential campaign, no debate organizers in either party have chosen to pare down the field. That might not happen for a while, so we’ll continue to see debates that include the one-percenters in both races. But is there any set-in-stone reason why some nonpartisan debate organizer could not invite the top three candidates from both parties — McCain, Giuliani, Romney, Clinton, Obama, and Edwards — to appear together at one debate? The cross currents at work in such an event would be fascinating, and the faithful from each party could assess their top prospects’ ability to handle the real opposition. This is a year of doing things differently, and there appears to be no reason, beyond the enormous political risks facing each candidate who participates, for the voters to have to wait until October 2008 to see Republican and Democratic ideas vie with each other on stage.