LeBlanc ran for the federal Liberal leadership himself back in 2008 before stepping aside for Micheal Ignatieff.
There had been speculation he might give it another shot but had not organised any sort of campaign team.
An insider close to Trudeau adds no pressure was put on LeBlanc to stand aside in favour of his childhood playmate. The Liberals will be choosing their new leader next spring.
Leblanc's father, Romeo was a longtime Trudeau cabinet member when Justin's father was Prime Minister and later served as Governor-General. He is also credited with saving the Admiral Beatty from demolition when it closed as a hotel before being turned into residential housing.