Political analysts marvel at Barack Obama's mastery of the Internet, where he has found many of his 1.5 million donors and created the social networking site my.barackobama.com to mobilize masses of young voters.

But they warn that the new and still evolving medium also poses serious risks for the Democratic presidential candidate, who, by opening his campaign to so many surrogates, is vulnerable to losing control of his message.

The Internet also has provided a forum for whisper campaigns such as one promoting the false assertion he is Muslim. White supremacist groups, too, have intensified their online rhetoric coinciding with the political ascent of a man who if elected in November would be America's first black president. Obama, an Illinois senator, will face Republican Senator John McCain in the general election.