From robotic telephone calls and e-mail to door-hangers and direct mail, campaigns have a wide variety of voter-mobilization methods at their fingertips. But according to two Ivy League professors, old-fashioned shoe-leather campaigning still beats out the more technologically advanced competition. "Face-to-face canvassing raises turnout by 7 to 12 percentage points," Yale University professor Donald Green told a group of activists earlier this summer. Moreover, door-to-door campaigning has a relatively low cost of about $19 per vote, said Green, who co-wrote, with fellow Yale professor Alan Gerber, a recently published book called "Get Out the Vote! How to Increase Voter Turnout." More expensive tactics, such as direct mail and certain types of phone banking, cost as much as $200 per vote. In addition to cost, face-to-face canvassing offers candidates other benefits, according to Green and Gerber's research in such states as Connecticut, California and Indiana.