And this is why Sarah Palin's dazzling star is finally starting to fade. Only slightly, but significantly enough to turn down the volume of the Republican cheer squad who have hailed her as the saviour of their political hopes. She is exciting, and likeable, but at the time of extreme economic uncertainty and an unpopular war, history tells us that American voters should revert to the issues, and seek wisdom over sass. It's not Palin's fault, of course, that Republican men are drooling over her, and that slogan writers think she is more electable as a "hottie" than a governor. Much of the coverage of her has been offensive, and marked with condescension about her lack of political pedigree, her lack of international travel and the fact she hails from a small town. It's just that the explosion of interest and the deafening hype about the gun-totin', moose shootin', mother of five from Alaska was bound to fade.

It's the nature of novelty. Her uniqueness made her irresistible - she so uncannily resembled some kind of kick-ass action figure, a beauty contestant turned political firebrand, that even many liberals confessed they'd like to spend a night eating mooseburgers with her. She entered a vacuum of information about who she was and what she stood for and suddenly was seen to embody archetypes such as Frontier Woman, Super Mom and Miss Congeniality on a Mission, before she was subject to any serious scrutiny. This is how she managed to inject steroids into the flagging Republican campaign, and excite those who either disliked or were unmoved by John McCain. Polling showed that she almost singlehandedly gave McCain a substantial bounce in approval ratings and that much of this was due to women. A Newsweek poll in July found McCain led Obama among white women by 44 per cent to 39 per cent. The most recent poll, taken last week, found his lead is now 53-37. It has been called the Palin effect - and given that women form 54 per cent of the active voting population in the US, it has made the Obama campaign very nervous. But there are three reasons why it is likely Americans will start taking a more sober look at the woman dubbed Sarah Barracuda. The first is she is now being seriously scrutinised, and her record as Governor is coming under criticism: she had great populist appeal but was known for cronyism and is being investigated for firing the Alaskan public safety commissioner after she had placed pressure on him to sack a state trooper who was her sister's ex-husband. "Troopergate" may be damaging given she has indicated she may refuse to co-operate.

The McCain campaign has limited her contact with the media and has planned only a couple of interviews with selected anchors. After an interview with ABC's Charlie Gibson last week, where she appeared awkward and stumbled over the meaning of the Bush doctrine, whether she would approve a pre-emptive strike on Pakistan and how being able to view Russia from Alaska might help her negotiate with Russia, polls showed a quick and dramatic dip. The second reason is that she lacks experience. In the Newsweek poll, half said they did not think she was ready. Even conservative commentators are expressing qualms about her preparedness to lead. The columnist George Will worried that the oldest man to embark on a first presidential term had chosen a person with "negligible experience".

David Frum, a former speechwriter for George Bush, pondered how serious McCain could be about national security to place it in the hands of a neophyte? The third reason that the Palin effect will likely diminish is that the economy will decide this election. This is the case for women especially - in a recent Zogby poll 65 per cent of women identified jobs and the economy as their most important issues, compared to 47 per cent of men. With the news of a deepening crisis this week - the bankruptcy of Lehman Brothers, the distressed sale of Merrill Lynch, the multibillion-dollar bail-out of American International - these sentiments will only grow more acute. The challenge for Obama and McCain is to establish their economic credentials and ensure the American public understands exactly how they might improve their lives. And knowing that your VP can make mooseburgers from beasts she shot herself may be of little comfort if you don't have a roof over your head.

Julia Baird is a senior editor at Newsweek.