Part 3 of NY1's series "The Contenders" focuses on Bill de Blasio's work with the Dinkins administration, President Bill Clinton's housing department and Hillary Clinton's Senate campaign in New York, which helped lay the groundwork for a career as a politician. NY1's Grace Rauh filed the following report.

In 1984, after graduating from New York University, Bill de Blasio made an important friend while working on Walter Mondale's campaign for president: Herbert Block. Block went on to work for then-Manhattan Borough President David Dinkins, who ran for mayor in 1989.

"We needed good people to work on the campaign, so I called up Bill," Block said.

De Blasio worked as a field and volunteer coordinator on the Dinkins campaign. He joined City Hall as an aide to Dinkins' political guru, Bill Lynch.

"He was a key, sort of, Bill Lynch used to call it ADT, any damn thing, any damn time guy that would be, you could give any assignment to and just get it done," Block said.

The job was important not only for professional reasons, but personal ones as well. De Blasio met his wife, Chirlane McCray, while working at City Hall.

"He always tells me I'm responsible for the kids he's got," Dinkins said.

After Dinkins lost in 1993, De Blasio landed a job at the Department of Housing and Urban Development.

He ran Bill Clinton's campaign operation in New York in 1996, and he was tapped to be the regional director for the federal housing agency, working under its secretary, Andrew Cuomo.

However, it was de Blasio's management of Hillary Clinton's Senate campaign in 2000 that solidified his reputation as a sharp political player and an aggressive advocate.

"She's taken on a lot of tough fights, and she's never shied away from the tough fight," de Blasio said about Hillary Clinton in 2000.

In the end, though, de Blasio was pushed aside within the campaign. His role narrowed as he focused more on helping Clinton in New York City.

"This was a really unique campaign, one with far more pressure than most," said Matthew Hiltzik, a former Clinton campaign aide. "And in that environment, it's people understanding what role they can play and how they can make a difference and what purpose they can serve, and he did that extremely well."

After Hillary Clinton was elected to the Senate, de Blasio made a big decision. Instead of running other people's campaigns, he decided to run his own.