In the article on McCain choosing Palin for VP, this is telling couple of paragraphs:

Republicans said that McCain hoped to blunt Obama’s message of political change with his pick, and it appeared likely she could remove all doubt about her home state in the fall campaign.

Obama has targeted Alaska and its three electoral votes, one of several he hoped to turn competitive in the fall despite its long tradition of voting Republican.

The fact that either candidate is concerned with Alaska and its three electoral votes portends a close contest this November.