The "nowcast" odds from http://fivethirtyeight.blogs.nytimes.com:
The "forecast" odds:
The "nowcast" odds are Nate Silver's guesses of the chances of an Obama or a Romney win if the election were held on a particular day. The "forecast" odds are Nate Silver's guesses as of a particular day of the chances of an Obama or a Romney win on November 6.
There are two reasons for the "forecast" odds to deviate from the "nowcast odds":
Stuff will happen to change public opinion between a particular day and the election, and (as long as Obama has the lead) a given shift of support in Obama's direction raises his odds by less than the same shift of support away from Obama's direction lowers his odds.
Public opinion is under pressure to return to what Nate Silver guesses is its "fundamental" level as generated by economic conditions.
Right now these two factors work to raise Silver's guess of Romney's odds from 24.8% in the nowcast to 27.1% in the forecast.
As time passes both of these factors diminish, because there is less time for the distribution of public opinion to spread and less time for the distribution's center to return to its "fundamental" level.
In the Silver-view, four things of note have happened in this presidential campaign:
The conventions--the fact that the Democrats put on an impressive convention while the Republicans did not, which shifted Obama's edge from marginal to substantial.
The period from early September to early October in which Obama's odds slowly rise not because of anything that happens to public opinion but rather because one of the two months in which Romney could change people's minds passes without him doing so.
Obama's catastrophic first debate in early October, and the consequent collapse of Obama's edge to marginal.
A subsequent partial recovery in the middle third of October.
If you have been covering the horserace, and if you have been writing about anything other than these four events--well, then, you have been wasting your and your readers' time.
Better for everybody if you had gone quail-hunting in Texas with Dick Cheney.
Better still if you had been writing stories about the Democratic Senate edge, or what will happen in the House, or about why the demographic groups of America support the candidates that they do.
I think that it is the fear among so many horserace journalists that after November 6 their bosses will point out that they are expensive, ask them to justify themselves, and that they will then be unable to--that that is driving the desire of so many horserace journalists to cast themselves as the villains from "Moneyball"…