Be afraid. Don't be very afraid. Be a little afraid, in the way perhaps you were when you first saw The Exorcist, unable to look at the screen but cosseted by the knowledge that once the closing credits rolled, the terror would pass with no residual damage done. Be that tiny bit afraid, please, and then lick your lips in gleeful anticipation that along with that delicious frisson of fear will come mirth and merriment beyond imagining. For her name is Sarah Palin and she's running for President.

Yup, she's started. More than two years before the first primary, Alaska's very own Cretina d'Evil has left the starting stalls already. Any lingering doubt that her campaign for the Republican nomination is under way evaporated this week, with the revelation that on Sunday she carved time from her frantic book-signing and publicity tour to go to North Carolina for scripture and Sabbath din-dins with Billy Graham. In the photo, she strokes the ancient preacher's right fist while her toddler Trig nestles on her lap, gazing at the 91-year-old presumably thinking: "I've no idea who you are, old timer, but if you can get the crazy lady who calls herself Mommy into the White House, you're all right with me."

Even with his red phone to heaven, Billy can't do that. No power in this world or the next, one hopes and prays, could. If you asked Jesus, he'd chuckle sardonically and say that, while he could do you some loaves and fishes, and at a pinch even a Lazarus, that one is beyond his pay grade. "I'd ask Dad," Christ might add, "but He'd only come over all Captain Mainwaring and call me a stupid boy."

So determinedly divisive a figure is the former Governor, so beset by suspicions of ethical dodginess, so ill qualified by intellect and temperament, so blinkered in her world view, and so shallow and self-serving in her every pre-scripted word and deed, that there must be more chance of the late Son of Sam taking the electoral college. To those queuing for hours in the freezing cold for her signature on Going Rogue, the mixture of whiny score-settling, half-truths, inventions and nauseating religiosity that constitutes newly published memoir, it looks different. To them and untold millions like them, she is a domestic political goddess, their reflection and representative in the big game. This is why, albeit in a drastically weak ante post field, she is the clear favourite to head the ticket in 2112.

"Like it or not," wrote Matthew Dowd, who knows a thing or two having helped Karl Rove got Dubya relected in 2004, "she has a shot". All she will need, he explains in yesterday's Washington Post, is to turn out a Republican base already in her pocket, to the horror of the Grand Old Party establishment, and win the early primaries Unstoppable momentum would then be hers.

That base has form here, having picked the exceedingly right-wing and sensationally unelectable Barry Goldwater in 1964. It is the loose equivalent of the Conservative membership (technically, the nutters in the country) which in 2001 glanced at Iain Duncan Smith and saw in him their Saviour. To these gin'n'Jag ostriches, heads burrowing into the sand in the search for that elusive time portal back to 1955, the fact that their party had just suffered a second landslide defeat because it was too insular, unpleasant and plain thick meant zilch. If William Hague's campaign medicine had made the country sicker than ever, they deduced, what finer remedy than to double the dosage?

Watching the Republicans precisely replicating this strategy is an almost daily delight to me, as also too (to borrow from Tina Fey's Palin parody) for Barack Obama. The vista of the GOP sinking deeper into the deranged clutches of Rush Limbaugh, Glenn Beck and Palin herself offers priceless reassurance while the Prez's popularity is sinking itself. If they continue on their present trajectories, in fact, the approval ratings of Palin and Obama will meet somewhere in the mid-40s very shortly. Not that they need the encouragement, but to the rednecks of the South and the come-over-say-hi-to-my-wife-and-Ma-and-sister-cos-she's-dyin'-to-meet y'all in the Appalachians, this must look like an oasis shimmering in the electoral distance.

That it has to be a mirage – that the reasons they worship her are the same reasons she could not carry any swing state with a sizeable percentage of Hispanic, black or college-educated voters – is beyond their concern or understanding, or both. These are the folks whose racist displacement activity is to affect the belief that Obama was born in Kenya, and buy wholesale her claim that universal health care means "death panels". Eighth wits at best, and vicious ones at that – only in hearing an echo of themselves in Palin do they show a keen grasp of reality.

As others have pointed out – and if you've turned to this page for an original thought, are you insane? – it is her status as the apotheosis of reality television that goes furthest in explaining her popularity. What is she, after all, if not the classic girl-next-door, plucked from obscurity (by John McCain) and turned into an ersatz superstar overnight thanks to a decent rendition of someone else's lyrics (that barnstorming Convention speech).

Like every canny X Factor contender, only to the nth degree, she sates the cravings of editors and their readers for tales of family triumph and tragedy, sex and sleaze. The good news here is that, while telegenic appeal and a knack for producing passable cover versions might give a contestant a shot at building a glittering career, it is never enough to maintain one. It can provide a couple of No.1s and sell pantomime tickets to the faithful who had your phone vote number on speed dial. But to last as a proper headline act takes more than a cute face, homespun verities, and incessant coverage in tabloids and supermarket magazines.

Sarah Palin has an alarmingly good chance of reaching the final two, but if ever she finds herself in a live debate with Obama, the lack of a real voice of her own and a shred of talent for more than slyly mirroring archaic prejudice will surely be terminally exposed.

If not ... if by some monstrous miracle she were to win, the sight of several billions projectile vomiting pea green puke like Linda Blair in The Exorcist will be something to behold.

So be afraid, but not too afraid, and stand by for the most surreal, extended and hilarious political melodrama in the history of this planet.