The poll of 830 likely voters also indicates 9 percent are undecided, while 3 percent prefer third-party candidates.
Field Poll Director Mark DiCamillo said McCain's choice of Palin to be his running mate has not helped him broaden the GOP base to include the non-partisans.
"He's made very little headway in that regard," DiCamillo said.
Among Republicans, about 28 percent of California voters said McCain's choice of Palin makes them more inclined to vote Republican, while 30 percent said it will make them less inclined and 40 percent said it will have no effect on their choice.
On the Democratic side, 60 percent of California voters said Obama's choice of Biden will have no effect on their vote, with 24 percent saying it makes them more inclined to vote Democratic and 14 percent saying less so.
The Field Poll, conducted Sept. 5-14, has a margin of error of plus or minus 5 percentage points among likely voters.
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