Raw traffic to a site may of course come from those against a candidate, as well as from supporters. However, features like "users also visited" on the sites like Alexa, Google and Quantcast suggest that this is likely not a major factor in the traffic rankings. Instead, they indicate that visitors to a given candidate's site also tend to spend time on other sites with political orientations similar to the candidate's own. Thus, visitors to Obama's site tend also to visit popular liberal/progressive sites, while visitors to McCain's site tend to favor well-known conservative sites. If the opposite traffic effect were sizable, there would likely be a more mixed list of also-visited sites.
Searching for answers
Search term frequency is obviously a useful barometer of online interest. How does it fare as a gauge of actual candidate support? The fact that a candidate's name is being searched on can indicate many different attitudes towards that candidate -- from avid support to mere curiosity to outright opposition.
This expectation turns out to be at least partly validated by the numbers. If we use Google's Insights for Search feature to look at the popularity of each presidential and vice presidential candidate's name as a search term, the results are largely similar to other results seen in this analysis, but with one very notable exception -- Sarah Palin queries.
For the terms "Obama" and "McCain" we see the same relatively sustained advantage for Obama that shows up in most of the traffic numbers. That said, from the point of McCain's announcement of her as his running mate, the search term "Palin" spikes far above the others in popularity -- and holds that lead throughout the better part of September, returning consistently below "Obama" and "McCain" only into October.
This is perhaps not so surprising if we consider the context: Palin is the only one of the four candidates who was largely new to the national political scene until her introduction to it precisely during the time period being studied here. It stands to reason that many online politics watchers (including presumably a good many prospective voters) would use the Internet to inform themselves about the newest name on the national stage.
Because of this context, we speculate that the gradual ebbing of searches on Palin's name to levels more in line with those of the other candidates reflects not necessarily particular pro or con judgments, but simply her growing familiarity to most Web users interested in the race. That said, it is notable that she remains, so far as Google searches are concerned at least, a figure of considerably more online interest than Obama's running mate, Joe Biden.