FiveThirtyEight.com: Drudge Poll Report Unreliable

Matt Drudge has been heavily promoting a poll on the Drudge Report that shows the presidential campaign is back to a two-point difference between Sens. John McCain and Barack Obama. But Nate Silver, writing for FiveThirtyEight.com, has noted in his blog that the poll is old and unreliable.

You may never have heard of the AP-Yahoo poll before. This is for good reason, since a look at the fine print reveals that it's not really intended for its horse race numbers (the AP uses a separate agency, GfK, for those).

For one thing, the poll is not timely. It entered the field on October 3 -- two weeks ago -- and left the field on October 13, which was this Monday.

For another thing, it's an internet-based poll: The survey was conducted using the web-enabled KnowledgePanelSM, a probability-based Panel designed to be representative of the U.S. population. Initially, participants are chosen scientifically by a random selection of telephone numbers. Persons in selected households are then invited by telephone to participate in the webenabled KnowledgePanelSM. For those who agree to participate, but do not already have Internet access, Knowledge Networks provides at no cost an Internet appliance and Internet service connection. People who already have computers and Internet service are permitted to participate using their own equipment. Panelists then receive unique log-in information for accessing surveys online, and then are sent emails three to four times a month inviting them to participate in research.

For a third thing, it has no likely voter screen, and the horse race question does not even appear to have a registered voter screen ... it's a poll of all adults.