In fact, Obama appeared to have been broadening in lead in most polls. Last week's CBS News/New York Times poll showed Obama with a 14-point lead. A Fox News poll out today has Obama up nine points. The Democrat leads by ten points in the Reuters/C-SPAN/Zogby poll and is up ten points and 9 points respectively in the NBC News/Wall Street Journal poll and the ABC News/Washington Post poll. On the other hand, a new GWU/Battleground poll has Obama up just two points.
So what are we to think of some of these wildly fluctuating poll numbers? Well, first, it's important to remember that every poll is simply a snapshot in time and that each poll measures voter intent slightly differently – whether it's how they identify likely voters, how they "weight" the results or how some questions are asked (although the "horserace" question is pretty straightforward.
In its write-up of the poll today, the AP put it this way: "Polls are snapshots of highly fluid campaigns. In this case, there is a margin of error of plus or minus 3.5 percentage points; that means Obama could be ahead by as many as 8 points or down by as many as 6. There are many reasons why polls differ, including methods of estimating likely voters and the wording of questions." Statistically speaking, a very small percentage of polls will simply be wrong.
Because of those factors, the most valuable and important indicator is the trendlines of each poll. Since the start of the conventions, the CBS News polls have registered a lead of 8 points for Obama following the Democratic convention, a tie, a 2-point McCain lead and then following that with Obama leads of 5 points, 5 points, 9 points, 5 points and 14 points. The next poll will show whether that later spread was an anomaly or a trend that is holding but the overall trend since the middle of September has shown a steady lead for Obama.
It's also useful to individually look at all polls taken around the same time frame because they are registering voter feelings in the context of the same general events. Obama has increased his lead in most polls since the completion of the debates and as the economic crisis continues to grip the country.
You can see the full rundown of polls at Real Clear Politics. The site also provides an "average" of polls, both at the national and state-by-state level but lumping different polls together does not provide an accurate view of the current state of the race. Because polls use different methods as explained above, averaging them together is like comparing apples and oranges, oil and water or dogs and cats. Also, some polls are conducted via methods not accepted by many others in the community, such as auto-dial polls which use computer systems instead of human beings to gather voter preferences. Because of those factors, some of the polls listed at Real Clear Politics are not recognized or used by CBS News.
Bottom line – look at the trends of individual polls, different polls taken around the same period of time and realize that campaigns can be fluid and that polls can be too.