Source: Reuters _____________ In 2004, YouTube didn't exist. Three years later, politicians have learned to fear and revere the video-sharing Web site that has become a vital part of the campaign for the 2008 U.S. presidential election. From rapid dissemination of political blunders, often with funny tunes, to a new wave of music videos featuring scantily clad women singing the praises of their presidential favorites, YouTube.com has sparked a new interest in politics. More than 2.5 million people have viewed "I've Got a Crush...On Obama" about Democratic Sen. Barack Obama since it was posted last month. A rebuttal video of women fighting over Obama and leading Republican contender Rudy Giuliani has been watched more than 500,000 times in four days.