All of the polls suggest that it is possible only two or three candidates could reach the 15 percent viability needed in any individual congressional district to earn delegates. That would make it possible for Mr. Sanders to win half the delegates in the state even if he wins only one-quarter of the total vote. And all of the polls suggest one group is helping Mr. Sanders’s numbers: Latinos, particularly young Latinos, whom the campaign has aggressively courted.

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What do the demographics of expected voters tell us?

There are more than 6 million no-party-preference voters in the state, a figure that skews younger, suggesting that many California voters don’t align with either party. Roughly 53 percent of the expected 14.5 million voters will be white voters, compared with about 26 percent Latino, 15 percent Asian-American and 6.5 percent black voters, according to a forecast by the Latino Policy and Politics Initiative at the University of California, Los Angeles.

How has the state’s shift to an earlier primary affected the race?

California has long been a political A.T.M. for both parties. But this year’s Democratic primary has made it so that candidates are focusing in on areas that have long been ignored — including the Inland Empire and the Central Valley. The primary is not a winner-take-all contest: Delegates are awarded based on how candidates do in each of the congressional districts. So, for example, Mr. Bloomberg has focused much of his investment on Orange County, where Democrats flipped several congressional seats in 2018.

Who has spent the most money and time in the state?

Mr. Sanders has held several high-profile rallies in the state over the last several months, including recently in Santa Ana, and a pair in San Jose and Los Angeles on Sunday. Mr. Biden, by comparison, has kept a relatively low profile in the state, and has not invested much time or energy in field operations in the state either.

Nobody has put more money into the primary than Mr. Bloomberg, who has also spent lavishly in the state, sending millions of campaign mailers to voters daily for more than a week. Mr. Bloomberg has spent more than $66 million on television so far, according to Advertising Analytics, an amount that drastically dwarfs all other candidates. Tom Steyer, who dropped out of the race after the South Carolina primary on Saturday, spent $32 million on television, compared with Mr. Sanders’s nearly $7 million. While Ms. Warren did not spend her own campaign money, a super PAC supporting her spent roughly $3.6 million.

Who has received important endorsements?

Many of the state’s most high-profile politicians, including Gov. Gavin Newsom, have stayed neutral since Senator Kamala Harris dropped out of the race late last year. (Though his wife, Jennifer Siebel Newsom, backed Ms. Warren on Friday.) Ms. Harris herself has not made any public comments about the remaining candidates, and neither has Jerry Brown, the popular former governor and former presidential candidate.