File - In this Dec. 11, 2019, file photo, Democratic Presidential candidate and former New York City Mayor Michael Bloomberg gestures while taking part in an on-stage conversation with former California Gov. Jerry Brown at the American Geophysical Union fall meeting in San Francisco. In the battle for the Democratic presidential nomination, no prize is bigger than California, which offers more delegates than any other state. And as candidates plot their strategies here, there's an overlooked group of voters who could be key to victory: independents. (AP Photo/Eric Risberg, File)