SACRAMENTO, Calif. (AP) - A new Field Poll shows Gov. Jerry Brown maintaining a commanding lead in his bid for an unprecedented fourth term. The survey released Thursday shows the Democratic incumbent leading his Republican challenger, Neel Kashkari, 54 percent to 33 percent among likely voters. Democrats also appear poised to again sweep all partisan statewide offices. They are leading their Republican opponents by margins ranging from seven to 13 percentage points. The poll found the two candidates vying for state superintendent of public instruction are in a dead heat, although nearly half of likely voters remain undecided in what is officially a nonpartisan race. Both candidates are Democrats. The Field Poll surveyed 941 likely voters from Oct. 15-28. The poll has a sampling error margin of plus or minus 3.4 percentage points.