Wondering why some polls have Obama racing away with a 14 point lead, while others show a virtual tie? Alan Fram writing for the Associated Press has a nice set of answers to many question you probably have about polling and why things are looking a little crazy right now.

From the article:

Q: Don’t pollsters simply ask questions, tally the answers and report them?

A: No. After finishing their interviews - usually with about 1,000 people, sometimes more - they adjust the answers to make sure they reflect Census Bureau data on the population like gender, age, education and race. For example, if the proportion of women interviewed is smaller than their actual share of the country’s population, their answers are given more “weight” to balance that out. But some pollsters make these adjustments differently than others. And while most polling organizations including the AP do not modify the responses to reflect some recent tally of how many Democrats, Republicans and independents there are, some do.

Q: Are those the only changes made?

A: No. As Election Day nears, polling organizations like to narrow their samples to people who say they are registered voters. They often narrow them further to those they consider likely voters. That’s because in a country where barely more than half of eligible voters usually show up for presidential elections, pollsters want their polls to reflect the views of those likeliest to vote.

Q: Is that hard to do?

A: Quite hard, since no one will truly know who will vote on Election Day until that day is over. In fact, virtually every polling organization has its own way of determining who likely voters are.

Like many polling organizations, the AP asks several questions about how often people have voted in the past and how likely they are to vote this year, and those who score highest are considered likely voters.