"Since my time as Vice President, Kate has been a loyal and trusted adviser, through thick and thin," President Biden said in a statement. "She was a critical strategic voice from the very first day of my presidential campaign in 2019 and has been a key part of advancing my agenda in the White House.  The country is better off as a result of her hard work and I’m so grateful to her – and to her husband and two young children – for giving so much. Ben has big shoes to fill." 

This is a developing story and will be updated.