Given the differences among groups in this poll, turnout of course is essential. This survey anticipates turnout in the Democratic primary by 31 percent of the state's adult population, and by 27 percent in the Republican contest. Tighter turnout scenarios make no difference in the Republican contest (in which Mitt Romney has a broad lead), but indicate a slightly larger Clinton lead (albeit within sampling error) on the Democratic side.
Likely voter estimates can be one source of differences in polls, as can sample sizes; another potential factor is the level of so-called "undecided" voters, in reality a function of polling technique rather than true indecision.
ABC/Post polls have fewer undecideds than most others, given the context of the question -- asking whom likely voters would support if the election were today. This survey finds 3 percent undecided, compared with an average of 12 percent in nine other publicly released polls in New Hampshire in the past month.
METHODOLOGY -- This ABC News/Washington Post poll was conducted by telephone Nov. 29-Dec. 3, 2007, among a random sample of 592 New Hampshire adults likely to vote in the 2008 Democratic primary. The results have a four-point error margin. Sampling, data collection and tabulation by TNS of Horsham, Pa.