In any strategy which focuses on the importance of winning certain swing states, the Western States of Montana, Colorado, New Mexico, Nevada, and Arizona are states which should be looked at. I mention all five of these states however, because they have all swung at least once in the last four elections.
Although Arizona is not considered a swing state in 2008, it could be critical in 2012 depending on how the electoral votes are re-allocated.
In general, the blue states are likely to lose electoral votes as a result of the next census, but most of the above mentioned states will grow at a faster rate than other states; therefore, it is more significant that these swings states will gain electoral votes than that the blue states will decline in relative electoral strength.
The candidates tend to chose a strategy which ignores states that are not competitive. But is this really the best strategy? By ignoring California and Texas, Obama and McCain might be making a mistake, since they could be raising a lot of money in these states.
Finally look at Alaska: once considered a swing state, although it has leaned Republican, it has moved more into the strong states column for McCain because it is Palin's home state. But Alaskans for Obama know more about Palin than most of Obama's supporters and a visit there could be beneficial for Obama.
It wouldn't change the likely outcome of a McCain victory there, but it would accomplish at least three things.
1. He could raise money there.
2. It would make a good story on the evening news.
3. It could increase his chances of winning the popular vote, which doesn't help him win the election, but would make the fairness of the electoral college more of an issue.
The counter argument, is, of course, that such a visit would limit his time in critical states like Colorado.
By the way, if Obama does better in Nevada than in Colorado it would increase the likelyhood of a 269-269 tie which would result in Obama being elected by the House of Representatives and Biden being elected by the Senate, assuming a decisive victory for the Democrats in both bodies in November.
If such a scenario occurs and McCain gets more popular votes that Obama, don't be surprised to hear key Republicans talk about abolishing the electoral college and replacing it with a popular vote. Don't forget, however, that in all likelyhood this would mean that the election could be based on a plurality rather than a majority of the popular vote which I see as being opposed to the principle of being ruled by the "consent of the governed".
(adding Nevada, New Mexico, Iowa, and New Hampshire to the blue states results in a 269-269 tie)