Recently there was a poll of Obama against and unnamed Republican. It did not surprise me that the un-named republican won, nor does it worry me. I am almost certain that Obama will not only win, but easily win. I will go gurther and state that much of the reason why the current GOP candidates are unimpressive is that the impressive people know this (Rubio for example) and are waiting till they can run against Biden (or whoever the Dems pick after Obama).
Early polls, particularly "unnamed vs incumbent" rarely matter. There are a lot of reasons why, and I am going to go through them.
First, lets talk about the Unnamed vs named bit. As evidence, I quote South Park, "Every election is between a Giant Douche and a Turd". Half the reason people vote is not because they like the Turd, but because they can't stand the Douche. In effect, when you do an un-named GOP vs incumbent, the incumbent only gets all the people that love him, while the un-named gets all the people that hate the incumbent PLUS all the people that think they like the general politics of the GOP. Imagine that Herman Cain wins the GOP primary. If only 2% of americans are racist enough not to vote for a black man, than that 2% moves away from Un-Named to "won't vote". I am in fact willing to bet that 2% is more like 5%, considering the prevalence of the birther movement. All candidates have similar issues, for example Gingrich may lose family values voters, the two Mormons may lose religious voters, there are still people that won't vote for a women, etc. etc. One of the reasons McCain lost is that some GOP stalwarts did not like him enough to get out the vote, but neither did the independents favor him over Obama.
To win an election, you need to appeal to both your party's base and the independents, not an easy task for a real person to do. Un-named does it automatically, but named candidates find this difficult. One of Obama's strengths was doing this well, and I suspect he will do it again in 2012.
Now for the "early" part. Another factor is that election spending actually WORKS. It is estimated that Obama alone will raise more than $1 billion dollars, and that the 2012 election will have candidates spending $7 Billion. They are not spending it because they are stupid. You need to tell people what you stand for and what you want to do.
Obama hasn't spent much of his money, but his opponents have already started spending and campaigning. For example, the press made much of the fact that most of the second GOP debate was spent on attacking Obama, not each other.
So it is no surprise that after the GOP attacks and before Obama has started the fight, the GOP looks like it is ahead? The GOP has been spending the past 2 years badmouthing Obama, while Obama has said almost nothing bad about the GOP. That changes when the GOP picks a candidate.
Next lets talk about how voting patterns change. Early polls tend to be about name recognition as much as anything else. That is why Trump did so well before he announced he wasn't running. It is not that people actually liked him, but instead it was that they knew who he was. As an election continues, people start recognizing the names of both candidates and that no longer matters as much. Instead people start focusing on issues. So on early polls, the greater name recognition tends to lead, but not so much for later polls. This explains why celebrities are likelier to win special elections - the electioneering period is shorter, so name recognition counts more (say hello to the Governator before we say goodbye to him.) But in Unnamed Republican Vs Obama, well the Republican name is in fact more famous than Obama. Ten years ago, people did not know who Obama is, but they knew what a Republican was. Republican has a higher name recognition factor than Obama - but Obama will almost certainly have a higher name recognition than whoever the GOP actually picks.
Another point is that the popular vote is not how we elect the president. We do it through the electoral system, which is how Bush became president despite the fact that Gore won the popular vote. It is not enough to win the voters, you have to win the electorates. The GOP has turned a rather nice, agreeable man (who likes to settle problems with a beer) into a rallying call for partisanship. As such, the people that hate and despise him may be gathered into certain states. Their voting power may be diluted. We don't know.
As such it is quite possible that Obama pulls a page from George W Bush's play book and wins the electoral vote despite losing the popular vote.