But if Biden’s firewall ever cracks — and there are some signs it’s softening in recent surveys — it will likely start with young black women, according to interviews with a dozen African American female organizers, lawmakers and activists who are heavily involved in the Democratic primary election or closely tracking the mood of black voters.

Their consensus: No candidate, Biden included, has a lock on African American voters in key early primary states. And Elizabeth Warren is gaining traction among black female voters under 50, while Bernie Sanders has a significant following among young black voters as well.

The anecdotal reports from African-American activists on the ground offer a reason for skepticism that Biden has already clinched the Democratic Party’s must-win voting bloc. The state of play is more fluid than assumed, they said, offering hope not just to Warren but to other candidates hoping to mount a late surge in the primary should Biden collapse.