Just cuz the media said it doesn't make it true. Afterall, they never asked me for my opinion so why should I assume this poll represents "all" americans or even a majority of them?
Who said it's supposed to represent all Americans? As the title of the article suggests, it's an "insiders poll" of what they think will happen:
National Journal's latest survey of Democratic and Republican Insiders -- members of Congress, party activists, fundraisers, consultants, lobbyists, and interest-group leaders for whom presidential politics is an "all-engrossing topic" -- finds that Democrat Hillary Rodham Clinton and Republican John McCain continue to be viewed as the candidates most likely to clinch the major parties' 2008 presidential nominations.