A new poll shows US Democratic presidential candidate Senator Bernie Sanders leads his rival Hillary Clinton by one point before the primary elections in the US State of California.

According to a survey conducted by the Los Angeles Times and the University of Southern California (USC), among the 1,500 registered voters contacted from 16 to 31 May, 44 percent of Democrats said they would support Sanders and 43 percent said they would back Clinton in the state’s primary which will be held on Tuesday.

The poll confirms that the Vermont senator enjoys the support of younger voters by huge margins in advance of Tuesday’s primary even among Latinos and Asians, many of whom come from a large pool of voters who have registered for the first time in the weeks before the election.

“His base of support is young voters, low-propensity voters and [nonpartisan] voters. Not only does he have to turn them out by election day, but he has to educate all those nonpartisan voters to request a Democratic ballot,” said Dan Schnur, the poll director.

“That’s not to say he can’t pull it off, but this may be the biggest voter mobilization challenge California has seen in many, many years,” he added.

US Democratic presidential candidate Hillary Clinton speaks at a Women for Hillary organizing event on June 3, 2016, at West Los Angeles College in Culver City, California. (AFP photo)

California with 546 Democratic delegates up for grabs is considered as the most influential state and since Sanders needs 837 extra delegates to become the Democratic nominee, he is going to need to count on Democratic Californians’ support.

This is while the average of the 14 polls conducted in California so far this year testifies that Clinton consistently has a solid lead of between five and 11 percentage points.

The former secretary of state is now only 70 delegates away from victory and as the poll suggests the Vermont senator needs to pick up around 90 percent of the vote in California and leave Clinton with just 10 percent.

Sanders would also need spectacular wins on Tuesday in Montana, New Jersey, New Mexico, North Dakota and South Dakota to keep Clinton from winning the party’s nomination.