Scott Rasmussen offers his own analysis of what’s going on in the polls in Massachusetts. I find his thinking compelling:

First, all three surveys show Coakley right around the 50% mark. The Rasmussen poll has her right at 50%, while the Globe shows her three points higher and PPP three points lower. If Coakley is truly right around the 50% mark, then the race is hers to lose, and Brown’s best possible scenario is a very narrow victory.
Second, all the polls show that a lower turnout is better for Brown. In the Rasmussen poll, Coakley leads by nine overall, but Brown pulls to within two points among those who are certain to vote. In the Globe poll, Coakley leads by 17 overall, but among those who are “extremely interested” in the election, it’s 47% for Brown and 47% for Coakley. PPP shows a toss-up but suggests it’s close because of low turnout among Democrats.
Finally, the Globe poll and the Rasmussen poll show identical vote totals for candidates other than Coakley. The Rasmussen poll finds 41% for Brown and did not mention a third-party candidate by name. The Globe shows 36% for Brown and five percent (5%) for independent candidate Joe Kennedy. It’s interesting that both polls show 41% of the vote going to a candidate other than Coakley.

Should Coakley be nervous about losing? Yes. Should Brown be confident of winning? No.