Millions of New Yorkers go to the polls Tuesday to elect a new mayor, with left-wing progressive Bill de Blasio tipped for a landslide victory to replace billionaire Michael Bloomberg.

The 52-year-old public advocate and his black formerly lesbian wife promise a new style to a city transformed by 12 years of tough love under Bloomberg, who is not standing again.

De Blasio's campaign has left Republican rival Joe Lhota trailing in the dust, picking up on the worries of the economically vulnerable middle class and tapping into a once reliably Democratic electorate.

An NBC-Wall Street Journal poll on Monday gave him an historic 41-point lead over Lhota, putting him on course to be the first Democrat elected mayor of the biggest US city since 1989.

But, with turnout typically weak for mayoral elections, de Blasio used the final day of campaigning to urge supporters to make good on their promises and to go out to vote.

"You have to go into every neighborhood and tell people how much this matters," he said, pressing the flesh in his home borough Brooklyn in the early morning winter chill.

By trading heavily on public appearances with his wife Chirlane and teenage children Dante and Chiara, he has connected to ordinary families trying to make ends meet and a vastly diverse electorate.

His multiracial family has struck a chord in a city of great ethnic diversity: 33.3 percent of New York is white, 25.5 percent black, 28.6 percent Hispanic and 12.7 percent Asian.

If elected New York's 109th mayor, de Blasio promises to raise taxes to fund universal pre-kindergarten education and after school programs, and build 200,000 affordable housing units.

He wants to reform the "stop and frisk" policy, which critics say unfairly targets black and Hispanic minorities, but which supporters say has driven down crime.

He has campaigned hard on the gulf between rich and poor in a city with more than 440,000 millionaires but where 21 percent live in poverty on $30,944 a year for a family of four.

A year ago he was a relative unknown and fought off stiff competition to win the Democratic primary, one reason analysts say for his determined lead over Lhota today.

The city of 8.3 million has six times as many Democrat voters yet David Dinkens was the last mayor to win the race in 1989.

Before being public advocate, he was on the city council for eight years, a housing official under President Bill Clinton and managed Hillary Clinton's New York Senate race in 2000.

He has been endorsed by a host of New York celebrities, including actresses Susan Sarandon and Sarah Jessica Parker.

Yet there are questions about whether he has the experience to lead a city hall staff of 300,000 and a budget of $72 billion.

There are also concerns that New York politics will again fall victim to cronyism and election-cycles after Bloomberg, whose vast wealth left him beholden to no one, steps down.

Heath Brown, assistant professor of political science at Seton Hall University, said that de Blasio's biggest challenge would be to transition from campaign to governance.

"From Wednesday morning to January 1 the real hard task is figuring out how to transition into the job of being mayor," Brown told AFP.

Who he decides to appoint to key positions, how he decides to organize his administration and the priorities of his early policy agenda will be the three main tasks.

"I suspect, knowing he's a smart politician... he will surround himself with people with the experiences that he may lack so I would look to those key appointments," Brown said.

Bloomberg, who changed the law to win three terms in office, will go down as one of New York's most transformative mayors but leaves behind an electorate divided by his legacy.

There has been a continued reduction in violent crime and his aggressive public health policies, like banning smoking in bars and restaurants, have been copied in many cities.

He overhauled the city waterfront, widened green spaces, launched the popular city-bike program and restored business optimism after the attacks of September 11, 2001.

On Monday, New York Daily News endorsed de Blasio but "with worrying reservations and strong prescriptions" for the "monumental challenge of running America's largest city".

"Big doses of reality will soon force de Blasio to act on tough issues that he smiled past in the campaign and to revise ill-considered stances," the news website wrote.