At his National Action Network in Harlem, Reverend Al Sharpton promoted the idea while sharing the stage with the mayor's closest confidant - his wife, Chirlane McCray.
"We have the studies, we know that most of the brain develops in the years before Kindergarten," said McCray.
After the rally, Mayor de Blasio met privately with local clergy and pitched his plan, which rests on taxing New Yorkers earning more than $500,000 per year.
"I think we've shown that there's tremendous public support for full day Pre-K and for after school," added de Blasio, "the name of the game is building support; it's a democracy and the more public support for an idea, the more likely it's going to pass."
De Blasio is hoping public support will convince lawmakers in Albany who are lukewarm to another tax, to get onboard. Governor Andrew Cuomo supports universal Pre-K, but disagrees on how to pay for it.
Governor Cuomo prefers using state budget funding instead of tax, something traditionally unpopular with voters, especially in an election year. Mayor de Blasio says his relationship with the governor has not chilled because of their disagreement.
"The dialogue has been very good, and very healthy," says de Blasio.
Elzora Cleveland has a 15-year-old daughter attending public school in Midtown. She says she paid for her daughter's Pre-K, because she felt it was important. She feels universal Pre-K is something that should be available for free to all families.
"I am very confident that it is coming our way," adds Cleveland, "if you teach children to love school at an early age, they will love school forever.
Mayor de Blasio will continue his Pre-K push on Sunday when he speaks at a church in the Bronx.