The Republican presidential candidates are scheduled to debate this afternoon on CNBC. This is a highly anticipated debate, since it will be the first in which Fred Thompson participates, and also the first since Mitt Romney began attacking Rudy Giuliani's economic record. And there are other noteworthy storylines as well. For example: Will John McCain continue to deliver strong debate performances? And will Mike Huckabee continue to charm audiences? Here's the thing, though. In addition to those five candidates, you will also have to listen to a bunch of guys who have no chance of winning the Republican nomination. They all will be competing for screen time. If Chris Matthews ignores one of those no chance candidates, the no chance candidates will scream for attention. So maybe this debate won't matter too much in the long run. Indeed, perhaps no debate will matter until the field is reduced to those candidates who have a chance at winning. If, that is, debates matter at all.