'The choice a presidential nominee makes for a running mate says a lot about him,' Mrs Palin told a flag-waving crowd at an airport hangar in the western state of Colorado.

'Senator Biden can claim many chairmanships across many, many years in Washington and certain many friends in the Washington establishment, but even those admirers would not call him an agent of change.'

The Republican ticket, solidified just this past week shortly after standardbearer John McCain chose Mrs Palin, the 44-year-old governor of Alaska, to be his running mate, has been trying to poach Democratic White House nominee Barack Obama's mantle of change by promising to reform Washington.

'Senator McCain has called the two of us a team of mavericks,' Mrs Palin said before describing how she cut wasteful spending and implemented ethics reform in Alaska.

'He's willing to shake things up in Washington and that's only one more reason to take the maverick of the Senate and put him in the White House.'

Mrs Palin, who was elected governor two years ago after fighting corruption in her own party, is popular among staunch conservatives and religious 'values' voters, but was widely unknown on the national stage before she was tapped for the ticket last week.

A new opinion poll showed American voters remained lukewarm about the self-described 'hockey mom', doubting her readiness for politics on the largest stage after a mere 20 months at her state's helm.

While six in 10 of those surveyed approved of Mr McCain's selection of Mrs Palin, only 42 per cent believed she had the kind of experience it takes to serve effectively as president if that became necessary, according to the ABC News poll.

Mr Biden, 65, passed the experience bar with 66 per cent approval, the same poll found. -- AFP