Instead of making the case that she would be an improvement on Obama, she'd have to explain why she would be preferable to former Massachusetts Gov. Mitt Romney, former Arkansas Gov. Mike Huckabee, Minnesota Gov. Tim Pawlenty or former Pennsylvania Sen. Rick Santorum, among other possible contenders.
It's one thing to Tweet your thoughts about Obama and Nancy Pelosi or endorse candidates on Facebook while hiding from skeptical reporters. It's another to match wits on issues with smart, well-informed, politically savvy conservative opponents who are determined to expose your shortcomings.
If Palin couldn't handle an interview with Katie Couric, how would she handle debates? Those come fast and furious in the primaries -- and both Romney and Huckabee can draw on their 2008 experience.
In that kind of setting, winks and one-liners won't take you far. Her opponents will ask her questions she would rather not answer, such as "Why were you for the Bridge to Nowhere until you were against it?" and "If you walked away from the governorship, how can we count on you not to quit the presidency?" They will also display a grasp of substance that Palin doesn't have and shows no interest in acquiring.
This last reality is a clue that those who want her to run will be disappointed. If she were serious about a White House bid, she would have spent the past two years making herself plausible as president. All Palin has done is make herself a major media phenomenon, as well as a wealthy woman.
Right now, she's a hot commodity that has soared in value and seems destined to get even hotter. But the same was once true of housing. Palin is another bubble, which a race for president would soon burst.