Zients left the White House in April after steering the administration’s pandemic response and leading the largest vaccination campaign in U.S. history. He returned to the White House in the fall to help Klain prepare for staff turnover after the midterms — a project that was ultimately limited in scope, as few senior staff members have left across the administration.

But, in recent weeks, Klain has assigned him different projects, which some viewed as preparing Zients for the top role, people familiar with the arrangement said, speaking on the condition of anonymity to discuss personnel matters.

Klain is expected to step down in the weeks after the State of the Union on Feb. 7, in what will be the first major departure from Biden’s inner circle.