Nate Silver does a very good job handicapping the presidential race this morning. (I recall some posters, one in particular, routinely discounted his predictions a year ago right up until the election, but he was right.) Of course, he doesn't claim to know what is going to happen, but he begins with the significance of Obama's relatively low approval rating at this time, 40-45%, which historically
indicates (not proves) that he is likely (not certain) to lose. That's a data point we already have. There are now, he says, two key variables to watch: the economy, and the nature of the Republican candidate and his distance from the mainstream.
Silver notes, to begin with, that the record of economic forecasting 12 months out is absolutely terrible, much worse, for instance, than trying to predict who is going to win next year's pennant. He also has some interesting comments about people who manage to find some obscure microeconomic indicator that has correlated well with the election results. That, he argues convincingly, is luck, the kind of luck out of which academic careers are made.
Basically, he thinks the economic variable is the most important. If the economy has a surprisingly good year--say 4% growth--Obama will almost surely beat any Republican candidate, including Romney. If the economy grows modestly--2% --Romney is a major favorite, but Obama would probably beat Cain or Perry. If the economy tanks, even Cain or Perry would probably beat Obama. (In an interesting footnote, he thinks John Huntsman would be by far the strongest Republican candidate but of course he has no chance.)
It occurs to me that Silver may have missed one important point. With respect to the economy he focused on what happened in the year before the election (although even that didn't save Bush I.) But unemployment has never been so high for so long in the entire period he is basing his predictions on. That could change the calculus, and not in Obama's favor.
There are, of course, wild cards, including potential shock headlines (the one I liked was, "Romney affair with Filipina maid--illegal immigrant received Romneycare.") Another is a Tea Party third-party effort if Romney is nominated. But in general, the message is clear: Obama needs some luck to win.