Barack Obama and John McCain have feuded and laid claim to being the authentic candidate of change and reform as their White House showdown roars into a frenetic eight-week final stretch.

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The McCain campaign meanwhile denied that his vice presidential pick Sarah Palin was “scared” to answer questions, following her failure to give a major interview or hold a press conference since her shock selection.

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Both presidential candidates are portraying themselves as drivers of change because most American votes are angry at the direction their country is headed and President George W Bush is highly unpopular.

Republican Senator McCain, striking out from his tarnished party, warned that Democratic foe Mr Obama did not have the “judgement” or record of reform or challenging his own party's dogma to be president.

“He never took on his party on a single major issue, I have taken them on a lot,” Mr McCain said on CBS program Face the Nation as the candidates launched a flurry of interviews in the heated run-up to the November 4 election.

“I think I can make a strong case that whatever the issue, he doesn't have the judgement. I have to make a strong case that I can bring about change,” Mr McCain said.

New direction

Mr Obama hammered Mr McCain back on the limping US economy in an interview recorded before the US government took over troubled mortgage giants Fannie Mae and Freddie Mac, saying the Republican represented no change from President Bush.

“John McCain, who is a good man and has a compelling biography, has embraced and adopted the George Bush economic platform,” Mr Obama said.

The Illinois senator argued that voters would realise that the election was a choice between a new direction and discredited Republican policies.

“If they like what they've had over the last eight years, then they'll go with McCain. And if they don't like it, hopefully they'll go with me,” he said on ABC's This Week program.

Mr Obama's running mate Senator Joseph Biden meanwhile said the idea that Mr McCain was a change agent was “malarkey”.

“Tell me one single thing they're going to do on the economy, foreign policy, taxes, that is going to be change,” Senator Biden said on NBC.

Palin 'not scared'

Both campaigns also sparred over Mrs Palin's failure to so far give a press conference or major interview since exploding onto the scene just over a week ago.

The Alaska governor was the only figure on either presidential ticket not to appear on a Sunday morning political television talk show.

“She will agree to an interview when she thinks it's time and she is comfortable doing it,” said Mr McCain's campaign manager Rick Davis on Fox News Sunday.

“She is not scared to answer questions. We run our campaign, not the news media. We'll do things on our timetable.”

Journalists are clamouring to interview first-term governor Mrs Palin amid claims by her political opponents that she is not ready or experienced enough to serve a “heartbeat” away from the presidency.

Senator Obama said Mr McCain's choice of Mrs Palin, who is beloved by conservatives, handcuffed the Republican presidential candidate to the legacy of unpopular President Bush.

Media 'piranhas'

“He chose somebody who may be even more aligned with George Bush, or (vice president) Dick Cheney or politics we've seen over the last eight years than John McCain himself is,” said Mr Obama.

Mr Biden said Mrs Palin, a 44-year-old mother of five, would be a “formidable” opponent, but that time was running out for her to flesh out her record.

“Eventually, she's going to have to sit in front of you like I'm doing,” Mr Biden said on NBC. “Eventually she's going to have to answer questions and not be sequestered. Eventually she's going to have to answer on the record.”

Mr Davis said that the media had not been fair to Mrs Palin during the political storm over her selection, and that the campaign had no intention of exposing her to “piranhas” in the news media.

With the full impact of last week's Republican jamboree not yet felt, a Gallup tracking poll has Mr Obama up by just two percentage points.

Rasmussen poll group had the race tied at 46 per cent, confirming Mr McCain last week squelched his rival's post-convention surge.

Obama, McCain duel as race gathers pace