Campaigns use statistics to determine likely election outcomes and evaluate campaign strategies.
Not all polls are created equally. Often details are buried in footnotes or omitted entirely in news articles that quote the poll. Be informed on how a poll was designed.A poll with a larger sample size is not necessarily the better poll. On the other hand, a sample size may be too small to state anything meaningful about public opinion.
Watch this About.com video to see how statistics are applied to political polling.