Mr. Rasmussen uses a telephone prompting system rather than live interviewers to survey respondents, a controversial technique. The third nightly tracking poll is Gallup, which has a good record even if its final 1996 survey overstated Mr. Clinton's winning margin by three percentage points. It currently shows Mr. Gore holding a four-point lead over Gov. Bush. Averaged together, the three nightly tracking polls show a one-point Bush lead. In recent years, election polls have often overestimated the Democrats' share of the vote.
People like to tell pollsters they plan to fulfill their civic duty and vote.
In reality, about one-third of people who say that won't show up. The best polls figure out if people are engaged enough to be likely voters. Even with those efforts, polls often oversample groups such as blue-collar women that end up not voting in high numbers. Turnout, which in 1996 fell below half of all adults, does matter. There are other reasons polls may tilt slightly toward Democrats.