Tonight’s debate is unlikely to have a meaningful impact on the race. At this point a major swing would require an externality such as a miraculous healing of the financial markets. Who will bring up Bill Ayers? I’m guessing Bob Schieffer, as a favor to McCain. (I was wrong. McCain went there first.)

Another remaining issue in the campaign is the size of Democratic gains in the Senate and House. A snapshot of current polls indicates 3-1 odds in favor of a 58-42 split. The principal alternate possibility is 57-43. These odds are easy to calculate, and I will present this again as the election nears. Silver thinks there’s a 30% chance of a filibuster-proof 60-40 split. This would require a 5-9 point swing for several Democratic candidates. His partisan stripes might be leading him to suggest more uncertainty than there really is. Developing.