Sen. Bernie Sanders achieved his first lead over former Secretary of State Hillary Clinton in a new USC Dornsife/Los Angeles Times poll released on Thursday. Sanders drew support from 44% of eligible Democratic voters, versus 43% for Clinton.

The result, within the poll’s 2.9% margin of error, is yet another statistical dead heat in the California primary — the fourth in less than two weeks. However, among voters with the highest propensity to vote, Clinton leads 49% to 39%.

The Times reports that Sanders is succeeding by winning among minority voters — who have, until now, been Clinton’s firewall:

Hillary Clinton’s popularity has slumped in California under an unrelenting challenge from Bernie Sanders, who has succeeded in breaching the demographic wall Clinton had counted on to protect her in the state’s presidential primary… As he has done across the country this primary season, Sanders commands the support of younger voters by huge margins in advance of Tuesday’s primary — even among Latinos and Asians, voter groups that Clinton easily won when she ran eight years ago. Many of his backers come from a large pool of voters who have registered for the first time in the weeks before the election.

Among Latino voters in particular, the poll shows a 44%-44% tie.

The question is what the turnout will be on primary day, June 7. Two-thirds — or more — of California primary voters have cast votes by mail in recent elections, and could have been voting since early May, long before Sanders’s late surge.

Sanders leads 48% to 35% among “non-partisan” voters. However, those voters will have to request a special ballot in order to support Sanders.

The poll also found that if Clinton is the nominee, 10% of Sanders voters in California intend to vote for Trump.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News. His new e-book, Leadership Secrets of the Kings and Prophets: What the Bible’s Struggles Teach Us About Today, is on sale through Amazon Kindle Direct. Follow him on Twitter at @joelpollak.