Similarly, numbers from Compete show the Obama campaign site serving about 64 percent of the total unique visitors to both campaign sites for the year ending in September. The graph shows that the Obama site has managed to sustain a large early lead built up during the protracted Democratic nomination contest, despite rapid growth by the McCain site as the general election campaign itself intensified over the US summer.
Quantcast had rankings similar to Compete's, with the Obama site sitting at #115 with around 7.9 million visitors, compared with the McCain site at No. 272 with around 4.3 million users (this matches with Compete's traffic split as well) . These Quantcast traffic trends also showed a "pinch" at the time of the Republican convention in an otherwise wide and relatively persistent gap. One additional point of interest in the Quantcast data is a noticeable widening of Obama's normal (pre-convention) advantage, starting sometime around the middle of September. Quantcast, at least, appears to show Obama pulling away.
The popular Alexa traffic tracking service tells a very similar tale. The Alexa service shows the McCain campaign site with a traffic rank overall on the Internet of 3,074 while the Obama site is ranked 869 overall. Comparing the two sites' traffic patterns using Alexa shows the same general trend, with the now familiar convention-related pinch and an otherwise sizable gap in Obama's favor. The Alexa data also -- like the Quantcast -- shows a discernable, widening of that gap starting around mid-September.
Sampling bias can be a concern in any measurement. While Alexa and Hitwise do have very large samples that would help guard against bias, Google provides an even larger pool of users. Using Google Site Trends we see once again the gap between the usage of the candidate sites
A deeper drill down into this Google-based trending reveals some interesting points. First, we see that when looking at the data on a day-to-day basis, there is a clear pinch in the trend lines on September 2 that is normalized out in the month-to-month view. This validates what we saw earlier in larger graphs when the Republican convention was finally in full swing.
Google data also shows that much of this traffic comes from the large population states. The lists below show the top 10 states, by traffic, for each candidate's site. It is interesting to see that some of the so-called "battleground" states (Florida, Virginia, Pennsylvania, Colorado) are represented at different positions in the two lists. What is most notable, however, is that you can see a consistent lead for Obama (represented by the blue horizontal bars) regardless of which candidate's top-10 ranking you use. That is, his site leads not only in all 10 of the states in which he does best, but also in the McCain site's 10 highest-traffic states as well.