When presidential candidates have a message they want voters to hear far and wide, they have typically turned to that old campaign standby: the television ad.

But as President Obama and his advisers prepare to begin their general election push, they are turning first not to a 30-second commercial but a 17-minute online documentary that they hope will be shared and spread online through social networks and e-mail.

When the Tom Hanks-narrated, Hollywood-style documentary, called “The Road We’ve Traveled,” is set to go online Thursday night, it will appear on a new YouTube platform that enables the Obama campaign to turn the passive experience of watching a video into an organizing and fund-raising tool. The technology will allow viewers to post campaign content to their Facebook pages, volunteer and donate all without having to leave Mr. Obama’s dedicated YouTube page.

Eventually campaign strategists hope to use the new software to focus on people in highly specific ways. For example, if someone watches a video about a certain geographic location, like Florida, a list of that person’s Facebook friends in Florida would appear alongside the video with a message from the campaign that suggests recommending the video to them.