These early bellwether states include: Indiana, Georgia, North Carolina, and Virginia. If Obama wins any of these, particularly one or more of the first three, it will be a blowout. Even if Obama is close in a place like Georgia, that is a good sign for him. If McCain can hold Obama off and sweep those states, it will likely be a much closer election than most pundits think.
You've heard of them before: Ohio, Pennsylvania, and Florida. If Obama wins two of three of these states, check mate. McCain needs a victory in all three, but a win in Ohio and Florida is a must. If he wins all three, throw all the conventional wisdom out the window.