Matthew Hindman

The Politico's Ben Smith has a story on Hillary Clinton's e-mail list, and its ostensible power.

 For political scientists, data on the effectiveness of political e-mail has been mixed at best.  Recent field experiments by campaign scholars have found that, compared to control groups, supporters who received candidate e-mail were not more likely to support the candidate, or to turn out on election day. 

But despite my initial skepticism, traffic data  suggests that e-mail has indeed become a powerful force in the 2008 presidential election. Consider the chart below.

This chart details Hitwise data on the percentage of traffic going to HillaryClinton.com and BarackObama.com directly from Webmail sites, such as Hotmail, Yahoo! mail, or Gmail:

 More thorough analysis of campaign traffic (including, hopefully, some cool new motion charts) to come. It should be emphasized that traffic to these sites explodes in January, February, and March, as the primary season shifts into gear.  Search engines are the other big drivers of traffic to campaign sites, particularly during months where the site audience is expanding.  

Still, indirect but powerful evidence that campaign email matters.  And that Hillary Clinton's email list may indeed be a valuable resource.