Bernie Sanders has won California, giving the candidate a piece of the largest share of Super Tuesday delegates to help him secure the Democratic presidential nomination, according to early projections.

His reported victory comes amid reports of long lines outside polls and high voter turnout as his campaign urges the state to keep polls open.

The state has the largest delegate count, a whopping 415, among nearly a third of all delegates up for grabs on Super Tuesday, though as in other states it's unclear how those delegates will be divided up among the candidates. Those delegates will vote to determine the party's nominee to face Donald Trump in the general election in November.

Mr Sanders spent roughly $7m on advertising in the state, and the campaign invested significantly on the ground as his grassroots support showed no signs of slowing. Volunteers knocked on a reported 1 million doors in California, and the campaign added 100 staff members and opened 23 offices.

His win in California follows two massive rallies in front of thousands of Californians on Sunday, including a Los Angeles rally in front of an estimated 24,000 people.

He told supporters on Sunday: "With your help on Tuesday, we're going to win the Democratic primary here in California. With your help, we're going to win the Democratic nomination, and with your help, we are going to defeat the most dangerous president in modern history."

Though he has amassed significant grassroots organising efforts in the state, his institutional Democratic support in California is more rare. The state's current and former governors have not endorsed a candidate, and neither has Kamala Harris, the state's star senator who dropped out of the presidential race late last year. Senator Dianne Feinstein endorsed Joe Biden, but Congressman Ro Khanna, who appeared with Mr Sanders at his San Jose rally on Sunday, is a co-chair of the senator's 2020 campaign.

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California Secretary of State Alex Padilla said the vote count is likely to carry on well into the night, as the state allows same-day voter registration and mail-in ballots.

Mr Sanders is likely carrying the state for the same reasons he saw success in neighbouring western states like Colorado and Utah, where significant numbers of young and Latino voters turned out to support the candidate, who has touted a multi-racial, working class-centered coalition supporting the campaign.