At first, no one thought she could be a contender. Ms Palin was far from the most gifted or experienced member of a crowded field of hopefuls: whatever her popular appeal, in the final analysis voters would surely remember the superior qualifications of her rivals and leave her disappointed. That was the conventional wisdom. But last night, the Palin juggernaut hit top gear once again – and it appeared to be on the point of proving the conventional wisdom wrong.
That description could apply to Sarah, Tea Party favourite, who was on the first stop of a nationwide book tour that some say is supposed to help her clamber back to the top of the pile of potential Republican presidential candidates. It applies equally well to Bristol, her daughter, who was due to compete in the final of the TV show Dancing with the Stars – and whose underdog appeal against far superior dancers is comparable to Ann Widdecombe's in Strictly Come Dancing. Last night, whether it wanted to or not, America was forced to acknowledge that Palins of all generations are a cultural force that simply won't go away.
If Bristol's rise can be dismissed as entertainment, her mother's relentless publicity drive has raised more fundamental questions. From her new cable reality show to her influence in the midterm elections, November has been Palin month. Is she occupying the media stage with such stunning success to give oxygen to a White House run? Or is she allowing speculation about her political future to rage to give oxygen to her media ventures?
"When she says that she is considering a run for the White House, everyone should take her seriously," said Nicolle Wallace, who was communications director in the Bush White House and a senior adviser to John McCain when he ran for president in 2008 with Ms Palin, then the Governor of Alaska, as his running mate. "She is the most important person on the Republican stage right now."
Her behaviour seems to support that theory. The former vice-presidential candidate's appearance in Phoenix, Arizona, last night began a nationwide tour that will include visits to states that come early in the presidential nomination process. And her book America by Heart: Reflections on Faith, Family and Flag takes Barack Obama to task, accusing him of misunderstanding how Americans think, of narcissism in power and of having an "average-to-below-average view of our country".
Boring European films, the exceptional wonder of America, and Bristol's virtues as a single mother are also features of the book, which hit the shelves yesterday. If there was any risk of fading from public view, help has come from 20-year-old Bristol, who has twirled all the way to the finals of Dancing with the Stars thanks to the votes of the viewers who have consistently overruled the judges.
The success of the younger Palin has brought even more publicity than it might because of allegations of vote-rigging. The suspicion is that Ms Palin's Tea Party fans are cheating by over-voting. The show's producers deny it.
Still, the enthusiasm of the family's fanbase seems unquestionable. And yet there are also reasons to be sceptical of a presidential run by Palin Snr. On the one hand, it has hardly gone unnoticed that two early states in the primary election circuit, Ohio and South Carolina, appear on her book tour schedule. Iowa, which will hold the first caucuses to help choose the nominees of both parties in barely 13 months from now, will have the benefit of two appearances, beginning with a book-signing in Des Moines this Saturday. Seemingly, however, she is going to Iowa without plans for what all the other putative candidates are already doing in the state: reaching out to local donors and Republican grandees.
It's why people like Mark McKinnon, also a former McCain adviser, are not so sure that the White House is in her sights. "I think the idea of a Sarah Palin candidacy is more attractive than the reality of one," he told The Los Angeles Times. "Right now she's got all the fame, money and influence one could possibly ever wish for with no accountability. Why throw all that away for the misery of a campaign?"
The book is already destined to be a best-seller. Like the television programme Sarah Palin's Alaska, it has the feel of having come from her heart, not from a ghost-writer. It is stuffed with homespun life-lessons and observations that the Tea Party folk – who get great praise from her pen – will devour.
Nor does Mr Obama get off lightly. "We have a President, perhaps for the first time since the founding of our republic, who expresses his belief that America is not the greatest earthly force for good the world has ever known," she writes. Of course, this being the Palins, it's family first. And although the book went to the printers long before the national debate started about Bristol and her dancing abilities, Sarah dwells at length on the glories of her daughter — if not as a performer, as a doting single mother. She proudly ponders her daughter's pluck in raising a baby boy, comparing her to television's Murphy Brown, the eponymous alcoholic journalist in the classic sitcom.
"Which is the more courageous course for a young, single mother: to sit down and shut up and avoid the critics," Palin asks her readers, "or to speak out in a painfully honest way about how tough single parenting is? I'm biased of course, but given a choice of role models between Bristol and Murphy Brown, I choose Bristol."
It might not be exactly the contest that the younger Palin found herself in last night. But in the long run, the cultural divide that the family has deepened may prove to be even trickier to navigate than those complicated dance routines.