“You did it all in the middle of the worst public health crisis since the Wilson era, with the smallest legislative majority of any newly elected Democratic president in a century,” Klain wrote.

Schumer, a New York Democrat, spoke by phone with Zients before the decision was officially announced and said the two agreed to maintain the “same close relationship with the White House Chief of Staff that I had with Ron.”

“He’s organized, focused, and deliberate, exactly the right person to lead the Biden administration and ensure the American people see and feel the benefits of these new laws,” Schumer, who often spoke to Klain by phone several times a day, said of Zients in a statement.

The balance of power is expected to be similar to the split portfolios of then-White House chief of staff Jack Lew and David Plouffe, a senior adviser to former President Barack Obama who managed political operations.

Klain has been mulling his exit since November’s midterm elections, according to a person familiar with the matter, who said people inside the White House have watched closely for clues as to his intentions.

Klain is known to email staff at all hours and even check on gas prices in the middle of the night – a work pace that many of his colleagues viewed as unsustainable in the long run.