The 2012 election is almost eighteen months away, but politics junkies are already being treated to polls asking if people plan to vote for Barack Obama in his re-election campaign, and testing how he fares against specific Republican opponents. What can these polls tell us so far ahead of the election, and what opportunities—or perils—do they create for reporters? To find out, CJR contributor Greg Marx recently corresponded over e-mail with John Sides, a professor of political science at George Washington University who, along with his colleagues at The Monkey Cage, was recently named “Blogger of the Year” by The Week. Their exchange is below.

Let’s start with the big picture: How much value do these polls have this far in advance? How much can they tell us about how the public views Obama or the Republican candidates—and what’s the relationship between those views now and what they might be next year?

The simplest fact about polling a presidential general election is this: early polls are much worse at forecasting the outcome than later polls. In some cases, early polls can at least be pretty good: when a popular incumbent is running for reelection, it’s not hard to forecast that he’ll win. But in other cases, it’s much more difficult to use polls to forecast outcomes. I pay relatively little attention to early polls. I am watching presidential approval and changes in macro-economic indicators.

What about the different ways of asking trial heat questions? Of course, when you pit Obama against any specific Republican opponent, how well that Republican does depends a lot on name recognition. This is why, for example, Romney tends to poll better against Obama than Pawlenty or Huntsman. And even Romney himself isn’t as well-known as he will be if he becomes the nominee. So his poll numbers will increase as well. In sum, barring some catastrophe, there’s every reason to anticipate a race that’s closer than 2008, because of the economy among other things. I don’t think we need polls to tell us this.

What are some factors that might influence early polls? Are there points in the campaign at which those factors tend to balance out, and the polls become more predictive?

Early poll numbers for the incumbent president or his party’s nominee are driven by the state of the country and approval of the incumbent. And, as I suggested before, they depend on how well-known various candidates are. As the campaign goes on, the polls do become more predictive of the outcome. Here is some forecasting research by Christopher Wlezien and Robert Erikson (pdf) that makes this point. Looking at the 1952-2000 presidential elections, they find that polls begin to be predictive of the outcome—over and above the predictive effects of the economy and presidential approval—in July of the election year, and then their impact increases with time. Obviously, on the eve of the election, the polls will typically predict the winner with great accuracy, although at that point you don’t need a poll to tell you who’s likely to win.

One of the insights of political science is that most people—and many voters—don’t follow politics very closely, especially when there’s not a major election on the horizon. At the same time, we’ve entered a period that’s often described as a “permanent campaign,” where the process of legislating takes on the characteristics of campaigns and the actual campaigns themselves seem to start earlier and earlier. Is there any reason to think this shift affects the utility of early polls—for example, by increasing the amount of information voters receive?

Greg Marx is a CJR staff writer. Follow him on Twitter @gregamarx.