New York Sen. Hillary Rodham Clinton has regained a double-digit lead over Illinois Sen. Barack Obama in the USA TODAY/Gallup Poll two weeks after the survey found the Democratic presidential rivals essentially tied.
The Democratic contest generally has been stable, though a USA TODAY Poll taken June 1-3 had shown Obama 1 percentage point ahead of Clinton, 30%-29%. In the new survey, Clinton leads Obama 33%-21% if former vice president Al Gore — who has neither entered the race nor ruled it out — is included among the candidates.
She leads by 39%-26% if Gore isn't included. Former North Carolina senator John Edwards is then third at 13%.
The new poll includes 334 Democrats and 182 independents who lean Democratic. Penn says including independents contributes to a survey's volatility because those voters are less committed to a candidate as well as less likely to vote in party primaries.
Frank Newport, editor in chief of the Gallup Poll, said the previous poll "either picked up a short-term change or … was a function of unusual sampling, which happened to pick up Democrats who were more pro-Obama than the underlying population."
The NBC News/Wall Street Journal poll and the Quinnipiac poll last week reported findings similar to the new Gallup survey. Both showed Clinton with a 14-point lead and Thompson tied with or ahead of McCain.
The USA TODAY Poll, taken last Monday through Thursday, has a margin of error of +/—5 percentage points among the subsample of 516 Democrats or Democratic-leaning independents.
http://www.usatoday.com/news/politics/2007-06-17-clinton-poll_N.htm