Clinton has the support of 41% of likely Democratic primary voters, according to the survey, which was taken over a seven-day period following the Labor Day weekend and released Thursday. Her closest rival is Illinois Sen. Barack Obama, who has 23%. Former North Carolina senator John Edwards is at 14%.

The poll shows Republican voters to be more divided. Giuliani, the former mayor of New York City, is slightly ahead of the GOP pack, with 22% of likely primary voters saying they will support him.

Former Massachusetts governor Mitt Romney is at 16%, as is former Tennessee senator Fred Thompson, who only recently joined the race. Arizona Sen. John McCain is at 15%. The margin of error is plus or minus 5 percentage points.

California Democrats allow independents to vote in their primary, although Republicans do not. The survey results reflect the views of 455 registered Democrats and independents likely to cast ballots in the Democratic primary and 353 registered Republicans likely to vote in their party's primary. Both contests will be held Feb. 5.

PPIC is a non-partisan think tank based in San Francisco. The poll results were based on a telephone survey of 2,003 California adult residents who were interviewed from Sept. 4 to Sept. 11.