This is a case of Drudge Cherry Picking the polls that advance Sen. McCain. The Gallup organization actually has three polls actual polls. The other two are
Registered voters: Obama 50 McCain 43
Likely Voters (Expanded): Obama 51 McCain 45
It seems to me that the gallup organization is hedging their bets in producing these three seperate polls. I wish they would make up their mind and produce one.
In terms of polling analysis from a mathematical standpoint, fivethirtyeight.com is far superior to drudge.
The Princeton Election Consortium is interesting also.
http://election.princeton.edu/