Allahpundit makes an interesting point:
[A]s things stand, [Palin is] a threat to win the GOP nomination but an almost certain loser in the general election unless economic conditions have deteriorated to the point where any Republican would be a threat to knock off Obama. But if any Republican would stand a good chance of winning, why would the GOP nominate the one Republican who would galvanize the Democrats in opposition? The more beatable Obama looks, the greater the temptation will be to nominate an inoffensive “electable” candidate like Romney and make the election a referendum on The One’s record; the less beatable Obama looks, the greater the temptation to roll the dice and nominate a lightning rod like Palin who can draw media attention away from Obama.