Why did McCain choose Palin as his running mate for the 2008 Republican Presidential ticket? I'll say that McCain's campaign was fooled by the Fox News Channel and others into thinking many millions of Democratic supporters of Clinton were fed up and would not support Democratic nominee Obama, and simultaneously had missed the general thrust of the campaign of his own supporters, who had spent months focusing the relative inexperience of Senator Obama.
The one place this worked as McCain expected was Arkansas. Between 2004 and 2008 roughly 50,000 voters shifted from the Democratic column to the Republican, the only notable increase for the Republicans that year. The exit polling shows that the entire shift, and then some, was among the women of Arkansas, since McCain did one percentage point worse than Bush among Arkansan men.