There has been a lot of attention today to one new poll showing McCain ahead nationally among "likely voters".
First of all, my usual caution, looking at national polls for a presidential election is just plain silly, and does NOT really tell you much of anything useful about the state of the race. We do NOT have a national election, we have 50 separate state elections (plus DC). So you are better off looking at something that breaks things down by state. I of course prefer my own analysis but there are a bunch of places out there that do this using a variety of different methodologies. If you actually care to understand what is going on, you need to look at the state by state breakdowns and pretty much ignore the national polling.
Having said that, if you MUST look at national polling, look at something that does a trendline over many polls, so that you don't get distracted by random noise or outliers. The best one out there (I think) is the one at pollster.com. First, you clearly see just how noisy the poll data is. Second, you see that this one result is a clear outlier.
Now, could additional polls start coming in any day now to reinforce the numbers in this new poll and thus indicate the beginning of a shift in McCain's direction? Quite possibly. But the point is that with just the one poll, with a large number of other polls continuing to give Obama a big lead, it is way too early to be saying anything of the sort. In fact, the trend at the moment is still a widening of Obama's lead.
Although, as I mentioned here and here and here there are some hints that some states may be starting to move in McCain's direction again after a long period of time where it seemed absolutely every update was good news for Obama.