Understand that small changes in a candidate's poll numbers that are within the poll's error margin are not significant and may or may not indicate a change. One New Hampshire poll might show Al Gore ahead, a second might have Bill Bradley in the lead and a third might indicate a Democratic presidential race too close to call. The same thing has been happening with Republicans George W. Bush and John McCain. The two races in the state with the nation's first presidential primary are very close, for one thing. Also, polls have an error margin, which means most of those polls generally are accurate within a specified range.
Pollsters use different techniques of deciding who to include in their poll.
Also, people still are learning about the candidates at this point in a campaign and sometimes are quick to change their mind. You're asking opinions about someone they don't know well. The opinions may be driven by last night's debate, a story they read in the newspaper, a grimacing photo on a magazine cover. Two New Hampshire polls this week offered an excellent example. The American Research Group has a tracking poll, a rolling average of three one-night polls, that keeps an eye on how the candidates are doing leading up to the Feb. 1 primary.