Double Speak

No matter which poll you look at, Martha Coakley's in a big slide. Her best case scenario, yesterday's Boston Globe poll, gives her a 15 point lead.
In three polls taken before the December primary that made Ms. Coakley her party's nominee, she had an average 29-point lead over Mr. Brown.
So her friends at the Globe show her lead having been cut in half. But lets get more realistic and average the three polls released over the past week together - that's Rasmussen, showing Coakley with a 9 point lead, Public Policy Polling (PPP) with a 1 point lead for Scott Brown, and the Globe Poll.
In three surveys taken over the last ten days or so, her lead has shrunk to an average of eight points. Ms. Coakley is ahead, but Mr. Brown is making a late surge. He can only hope it isn't stopped because previously apathetic Democrats respond to the polls by deciding to drag themselves out to vote.
So Coakley is leading by an average of 8 points, which means she's lost 21 points in the last few weeks. Nice. But previously apathetic Democrats can stay apathetic, given that the newspaper of record published their own poll without mentioning the poll from PPP making things look much worse for Coakley.
The Globe poll was taken over four days, finishing on January 6. The PPP poll began the next day and ended on January 8. So it's possible that PPP was picking up a late shift to Mr. Brown. But the more likely explanation for the mysterious "poll gap" is that special elections are a different breed of race for pollsters. Turnout is low and notoriously hard to predict, especially for a Massachusetts race in the dead of winter.
The key to polling a low turnout race is getting the turnout right, and figuring out who is going to turn out. The Globe apparently included voters who said they "May" vote in the special election January 19.
How to determine who precisely is a "likely voter" in such a race is almost an art form. The PPP survey, along with an earlier Rasmussen poll, predicts a lower turnout than the Globe does. PPP even told survey targets that if they didn't intend to vote, they should hang up. The Globe poll, which used live interviewers unlike the other two surveys, also found the race gets closer if it "tightened" its turnout screen. Among voters in the Globe poll who said they were extremely interested in the race, the vote was tied.
If she continues to lose ground at that rate, Attorney General Coakley will be toast. What helps Scott? The Patriots losing, unemployment holding steady, Harry Reid talking about Negro Dialect, and the health care debate dragging on. Obama days are scary days.