Which campaign has the hotter grass-roots? One way to answer that question is to search for local events being organized by volunteers around the country and see who's got more things going on.

The top three Democratic campaigns make this really easy to do, with "find an event" tools on their sites. You can find Obama events here, Edwards events here, and Clinton's is smartly located on her home page. I guess the other campaigns either don't have a clue, or are afraid that if they gave supporters the freedom to list events, no one would. As it is, my quick research shows "Team Hillary" looks a lot like a Potemkin village.

Events within 100 miles of New York, NY (10001)

Barack Obama: 40
John Edwards: 12
Hillary Clinton: 3

Events within 100 miles of Los Angeles, CA (90021)

Barack Obama: 45
John Edwards: 6
Hillary Clinton: 0

Events within 100 miles of Washington, DC (20036)

Barack Obama: 30
John Edwards: 6
Hillary Clinton: 2 (One of which is actually in Guangzhou, China!)

Events within 100 miles of Manchester, NH (03101)

Barack Obama: 36
John Edwards: 7
Hillary Clinton: 5

Events within 100 miles of Des Moines, IA (50301)

John Edwards: 6
Barack Obama: 3
Hillary Clinton: 0

A caution about these numbers: I did notice that some people are using these open event listing tools to advertise things that have nothing to do with supporting a candidate. For example, a group aiding the homeless is listed on Obama's site, as is someone promoting the 40th anniversary of Martin Luther King's "Beyond Vietnam" speech. People can report objectionable content to the Obama campaign, but I would estimate that no more than five to ten percent of the events listed on MyBarackObama.com are from free riders taking advantage of the site. Also, several of the Hillary Clinton events listed on her site as far off as late June.

My conclusion: Barack is hot; Edwards is warm, Hillary is not. But you probably knew that already.