It’s against this backdrop that Palin’s public pronouncements, culminating with her debate performance, have been so striking. The standard take has it that she’s either speaking utter ignorant gibberish (as to Couric) or reciting highly polished, campaign-written sound bites that she’s memorized (as at the convention and the debate). But there’s a steady unnerving undertone to Palin’s utterances, a consistent message of hubristic self-confidence and hyper-ambition. She wants to be president, she thinks she can be president, she thinks she will be president. And perhaps soon. She often sounds like someone who sees herself as half-a-heartbeat away from the presidency. Or who is seen that way by her own camp, the hard-right G.O.P. base that never liked McCain anyway and views him as, at best, a White House place holder.

This was first apparent when Palin extolled a “small town” vice president as a hero in her convention speech  and cited not one of the many Republican vice presidents who fit that bill but, bizarrely, Harry Truman, a Democrat who succeeded a president who died in office. A few weeks later came Charlie Gibson’s question about whether she thought she was “experienced enough” and “ready” when McCain invited her to join his ticket. Palin replied that she didn’t “hesitate” and didn’t “even blink”  a response that seemed jarring for its lack of any human modesty, even false modesty.

In the last of her Couric interview installments on Thursday, Palin was asked which vice president had most impressed her, and after paying tribute to Geraldine Ferraro, she chose “George Bush Sr.” Her criterion: she most admires vice presidents “who have gone on to the presidency.” Hours later, at the debate, she offered a discordant contrast to Biden when asked by Gwen Ifill how they would each govern “if the worst happened” and the president died in office. After Biden spoke of somber continuity, Palin was weirdly flip and chipper, eager to say that as a “maverick” she’d go her own way.

But the debate’s most telling passage arrived when Biden welled up in recounting his days as a single father after his first wife and one of his children were killed in a car crash. Palin’s perky response  she immediately started selling McCain as a “consummate maverick” again  was as emotionally disconnected as Michael Dukakis’s notoriously cerebral answer to the hypothetical 1988 debate question about his wife being “raped and murdered.” If, as some feel, Obama is cool, Palin is ice cold. She didn’t even acknowledge Biden’s devastating personal history.

Image Frank Rich Credit... Fred R. Conrad/The New York Times

After the debate, Republicans who had been bailing on Palin rushed back to the fold. They know her relentless ambition is the only hope for saving a ticket headed by a warrior who is out of juice and out of ideas. So what if she is preposterously unprepared to run the country in the midst of its greatest economic crisis in 70 years? She looks and sounds like a winner.

You can understand why they believe that. She has more testosterone than anyone else at the top of her party. McCain and his surrogates are forever blaming their travails on others, wailing about supposed sexist and journalistic biases around the clock. McCain even canceled an interview with Larry King, for heaven’s sake, in a fit of pique at a CNN anchor, Campbell Brown.