Chow resigned her seat last week to run for mayor of Toronto.
Cressy was president of the party riding association in Trinity-Spadina, but quit when he decided to seek the nomination.
He was Chow's campaign chair in the 2011 federal election and is also a member of the NDP federal council.
If elected, Cressy says he will build on Chow's legacy.
He says he will stress a progressive urban agenda and environmental and social justice at home and abroad.
Also on HuffPost