Sen. Barack Obama has opened up a 24 point lead over Sen. John McCain in California, according to a new Field Poll of voters likely to cast ballots in November's presidential contest.

Obama leads in every region of the state except the conservative Central Valley, where the Illinois senator trails by just one point, 40% to 39%. The Valley has the most undecided voters of any region at 21%.

Obama's overall lead is 54% to 30% in the state. His supporters are much more passionate, with 51% saying they are "very enthusiastic" about supporting their candidate, compared with 17% for Arizona's McCain.

Read all the poll results here.