As David noted below, many commentators have taken little more than an hour to proceed from slack-jawed bewilderment to belief that Sarah Palin's unexplained resignation may be a political masterstroke.

For the moment there's no clear evidence of or explanation for some massive political or scandal bombshell that would have driven Palin from office. And it can be difficult not to allow the preposterous to become credible when many supposedly rational people are saying it.

But logic and common sense seldom fail as a guide to understanding politics. And the idea that Gov. Palin just up and decided for no reason in particular to resign her office little more than half way through her term, with a hastily assembled press conference and a rambling and histrionic speech, is just too silly for serious consideration. Another sign of the confusion on the inside are the comments reporters are getting from supposed Palin insiders. Palin insiders told Andrew Mitchell that Palin was "out of politics for good." But she told the Executive Director of the Republican Governors Association that she's resigning to campaign for more candidates in the continental US, work on her book, all with an eye to gearing up for her run for president in 2012. Call me cynical but it seems hard to reconcile those two explanations.

As with her speech itself, the tell is that the decision was apparently so rushed and sudden that there was not enough time to come up with a plausible cover story or to get out the word about what it was.

It looks like a duck and quacks like a duck. Either Palin is resigning ahead of some titanic scandal (which should emerge in short order if it exists) or her resignation was triggered by an even more extreme mental instability than we'd previously suspected.