"Six in 10 voters see her (Palin) as lacking the experience to be an effective president, and a third are now less likely to vote for McCain because of her," said the poll conducted by The Washington Post and ABC News on Thursday.
The poll showed that nearly two-thirds of both independent men and women said Palin has insufficient experience to run the White House adding that the Alaskan governor might now be a drag on the Republican ticket.
When Republican presidential candidate John McCain chose Palin as his running mate on August 29, she was an unknown official for the US public.
She disappointed pundits after her interview with CBS's Katie Couric on Sept. 24 when she failed to convince viewers of her understanding of the country's ailing economy.
"The 60 percent who now see Palin as insufficiently experienced to step into the presidency is steeply higher than in a Post-ABC poll after her nomination early last month," the survey said.
On Thursday, Palin will meet her Democratic rival Joseph Biden in a vice presidential debate to ease doubts about whether she is up to the job.