His victory was never in doubt: De Blasio led his Republican rival by a wide margin in opinion polls throughout campaign

New York voters elected their first Democratic mayor for 20 years on Tuesday, picking Bill de Blasio to lead the city out of the unprecedented three-term reign of the billionaire businessman Michael Bloomberg.

News networks called the result for De Blasio, a 52-year-old self-described progressive, on the basis of exit polls as soon as voting ended at 9pm ET. His victory was never in doubt: De Blasio led his Republican rival, Joe Lhota, by a wide margin in opinion polls throughout the campaign.

De Blasio based his campaign on a portrayal of New York as a "tale of two cities", attention to the disparity between the haves and have-nots of New York City. He has promised to expand pre-kindergarten and after-school programs by raising taxes on high earners. It remains to be seen if De Blasio will be able to raise taxes, however, which requires approval from New York State in Albany.

He will be sworn in on 1 January when he will become the 109th mayor of New York City, replacing Bloomberg, a former Republican who ran as an independent. The city council allowed Bloomberg to run for a third term, controversially accepting his argument that in the wake of the financial meltdown, he should be allowed to continue leading the city. A two-term limit was later restored.

Follow our live blog coverage of tonight's results here

The last Democratic mayor of New York was David Dinkins, who became the city's first and only black leader in 1989. De Blasio worked on Dinkins' campaign 24 years ago, where he met his wife Chirlane McCray.

McCray and the couple's children, Dante and Chiara, featured extensively in De Blasio's campaign. Dante, 15, appeared in and narrated De Blasio's first television commercial.

De Blasio had been up by almost 40 percentage points in every survey conducted since he and Lhota won their respective nominations.

At De Blasio's victory party at the YMCA in Park Slope, Brooklyn, supporters were jubilant. Amina Abdul-Wahhab, 40, said: "It makes me feel great, I feel like there's gonna be a lot of progress, he's really fighting for the working class," she said. "We finally have a politician who is fighting for the everyday people."

Abdul-Wahhab lives in East Flatbush, around four miles from Park Slope but a world away in terms of average incomes. "There's a lot of working class people struggling just to make ends meet," she said. She said early childhood education was a key policy for single parents in the neighbourhood.

Leon Goldenberg, a real estate agent from Midwood, was "absolutely excited", despite observing that De Blasio's victory "seems to have been set in after the primary". He added: "You don't have the high you normally would when it's a close race," he said.

Asked how the city will change under De Blasio's leadership, Goldenberg said the change would "not nearly be as dramatic as people expect".

"There'll be a little less of the friction that the current mayor has caused," he said. De Blasio would be "less Manhattan-centric", and "hopefully there'll be more affordable housing", Goldenberg said.

De Blasio was not initially fancied to win his party's nomination ahead of his main rivals Bill Thompson, the city's former comptroller, and Christine Quinn, the city council leader. Quinn was the early favourite to be the Democratic nominee but De Blasio won 40.81% of the vote in the primary, winning the poll outright.

Lhota, the losing candidate, described himself as a "fiscal conservative and progressive socially". Throughout the campaign he attempted to portray De Blasio as soft on crime – "recklessly dangerous" on crime, one ad said – but his message failed to gain traction. In one of his final campaign acts Lhota criticised De Blasio after the Democrat admitted he was "not a morning person".

© Guardian News and Media 2013

[Image via MSNBC]