Washington (CNN) -- California Gov. Jerry Brown is leading his Republican challenger, Neel Kashkari, by a hefty 16-point margin, according to a new Field Poll released Thursday.
Brown, 76, who is seeking a fourth term in Sacramento, is favored by 50% of likely voters, compared with 34% for Kashkari. While Brown performs well among self-described liberals and Kashkari is strongly favored by self-described conservatives, moderates favor the incumbent Democrat by 32 points.
The new poll results were released shortly before the only scheduled debate between Brown and Kashkari. The two men are set to face off Thursday in Sacramento at 7 p.m. PT (10 p.m. ET).
According to the Field Poll, 58% of likely voters now approve of Brown's job performance, while 56% hold a favorable opinion of the governor.
Kashkari, an investment banker and member of George W. Bush's administration, remains a blank slate for many California voters. More than four in 10 likely voters have no opinion of the Republican nominee. Thirty-five percent of likely voters have a favorable opinion of Kashkari, compared with 24% who view him unfavorably.
Not surprisingly, Brown is maintaining his widest lead around San Francisco and Los Angeles, two Democratic strongholds. Kashkari is running narrowly ahead of the governor in the more conservative Central Valley.
Brown was first elected governor in 1974, at age 36. He won additional terms in 1978 and 2010. Between terms in the state's highest office, Brown also served as the mayor of Oakland and state attorney general.
Brown sought the Democratic presidential nomination in 1976, 1980 and 1992.
The Field Poll was conducted between August 14 and 28 among 467 likely voters. It has a sampling error of plus or minus 4.8 percentage points.