"This is a man who can give an entire speech about the wars America is fighting, and never use the word 'victory' except when he's talking about his own campaign." Ouch.

"Terrorist states are seeking nuclear weapons without delay … he wants to meet them without preconditions," she said. Kapow.

Palin, whose own thin record has been heavily scrutinised, was remarkably effective in turning the tables on Obama - dishing out some of the nastiest criticism of the campaign - and all with a smile. It's a style of politics with which she's familiar and comfortable. The New York Times talked this week to the man she defeated as mayor of Wasilla, Alaska in 1996, when she was just 32.

Until then elections in Wasilla - population about 9000 - were decided on issues such as whether to pave roads or install sewers, or who went hunting with whom. But that changed as Palin began her run against John Stein. Anti-abortion fliers circulated. Palin played up her church work and her membership of the National Rifle Association.

"Sarah comes in with all this ideological stuff, and I was like, 'Whoa'," Mr Stein told The New York Times .

"But that got her elected: abortion, gun rights, term limits and the religious born-again thing. I'm not a churchgoing guy, and that was another issue: 'We will have our first Christian mayor.' I thought: 'Holy cow, what's happening here? Does that mean she thinks I'm Jewish or Islamic?'," recalled Mr Stein, who was raised Lutheran.

There's no doubt that Palin will energise the base of the Republican Party. That much was evident in the excited faces of the party faithful after her convention speech. Senator Obama's message of change has energised younger voters in a way that has not been seen for a decade. His campaign has registered hundreds of thousands of new voters, notably young people and African Americans, in the urban centres in the big swing states.

In contrast, Senator McCain was struggling to provide a similar injection of enthusiasm - essential to ensure voter turnout in a non-compulsory voting system.

Despite describing himself as anti-abortion, McCain has stopped short of backing a constitutional amendment to protect unborn foetuses that the Republican platform calls for. He also voted in favour of embryonic stem-cell research. But with the Palin choice, the religious right of the party feels it has had a victory.

Palin shrewdly did not canvass her position on abortion during her acceptance speech, but she is said to be staunchly anti-abortion, even in the case of rape or incest.

Palin will play particularly well in small-town America, from where she hails.

"I had the privilege of living most of my life in a small town," Palin told the Republican crowd to huge cheers. "I was just your average hockey mum, and signed up for the PTA because I wanted to make my kids' public education better. When I ran for city council, I didn't need focus groups and voter profiles because I knew those voters, and knew their families, too," she said.

The presidential election is likely to come down to four or five big states: Ohio, Michigan, Pennsylvania, Florida, and Virginia.

The Democrats are also pursuing a strategy of trying to win over some Midwest states - states that the Republicans need to hold.

Among older, more conservative Democrats and independents Palin might just touch the right nerve.

"Governor Sarah Palin may well draw larger crowds than Senator John McCain ever did, and the McCain campaign plans to take advantage," Marc Ambinder, the Atlantic Monthly's columnist said on Thursday. "They're filling a calendar that will find her deployed to places where McCain can't go, places where McCain's gone and fallen flat, and places where social conservatives need an enthusiasm boost."

The challenge for the Obama team will be to work out how to counter her full-frontal assault on their candidate and then to bring her down a peg or two.

Obama's strongest argument remains that McCain, despite what he says about being a maverick, will give America another term of George Bush's policies. The economy remains the key issue with middle-class and poor Americans, who have seen average incomes decline by more than $US1000 ($1199) over the life of the Bush Administration.

The Democrats are offering a much more comprehensive safety net and a restructured tax scale that would almost certainly put more money in the pockets of most voters earning less than $US160,000 a year.

McCain has sought to define the economic issue as a question of who would best stimulate growth and as about tackling petrol prices. Here, Palin could be helpful - or dangerous. On the one hand as Governor of Alaska, she knows a lot more about the oil industry than most.

On the other, despite her claims to having stood up to big oil, there is evidence she took campaign donations from groups including VICO, the oil services company at the heart of a scandal which has led to the indictment of Ted Stevens, the Republican senator from Alaska.

She favours drilling for oil in the Alaskan National Wildlife refuge - which McCain has ruled out; she thinks polar bears should not have been put on the endangered species list, something McCain supports; and she has been sceptical about the impact of global warming - in contrast to McCain, who has promised to act swiftly on climate change.

Palin also highlights McCain's age. At 72, it is more than academic to speculate that McCain could die in office, with actuaries putting it at a one-in-three chance. No matter how hard the Republicans spin her experience as equal or better than that of Obama, her readiness for office remains a serious doubt in some voters' minds.