Nate Silver has released his first election forecast:
Mr. Obama remains slightly ahead of Mr. Romney in most national polls, and he has had a somewhat clearer advantage in polling conducted at the state level. Mr. Obama would be about 80 percent likely to win an election held today, according to the model.
However, the outlook for the Nov. 6 election is much less certain, with Mr. Obama having winning odds of just over 60 percent. The forecast currently calls for Mr. Obama to win roughly 290 electoral votes, but outcomes ranging everywhere from about 160 to 390 electoral votes are plausible, given the long lead time until the election and the amount of news that could occur between now and then.
You can read much more on his methodology here.