Presidential debates are important -- and the first debate is the most important of all, establishing an arc of opinion that persists unless jarred loose by big mistakes or dramatic events.

So whether this year's first presidential debate between Sens. Barack Obama and John McCain is Friday night or postponed a few days, it may be the fall's most critical event. In the nine first debates since 1960, the perceived winner of the debate averaged a 4.2 point net swing in the Gallup poll.

Mr....