Former US President Bill Clinton (L) introduces newly elected New York City Mayor Bill de Blasio (C) and his wife Chirlane McCray at City Hall in New York January 1, 2014. [Photo/Agencies]

HAVES AND HAVE-NOTS

Even beyond his ambitious, liberal agenda, de Blasio faces the day-to-day challenges of running a city of more than 8 million voters. He has just a few months to craft his first budget and his administration will be tasked with negotiating new contracts with each of the city's public-sector unions, all of which have been working under long-expired terms.

A major winter storm is due to hit the city on Thursday, perhaps offering de Blasio his first major test.

But while Bloomberg often clashed with the City Council and with more liberal citywide officials, de Blasio will be surrounded by allies. The city's new comptroller, Scott Stringer, and its new public advocate, Letitia James, both echoed de Blasio's theme of confronting inequality.

"The growing gap between the haves and the have-nots undermines our city and tears at the fabric of our democracy," said James, a former city councilwoman who is the first black woman to be elected to citywide office in New York City.

De Blasio began his career in government working under David Dinkins, the city's first black mayor who was elected in 1986 and was the last Democrat to hold the post.

In 2000, when former US first lady Hillary Clinton ran for US senator in New York, de Blasio was her campaign manager.

He went on to serve two terms on the New York City Council and four years ago was elected public advocate - a citywide office with a budget of just $2 million that is generally seen as a springboard for the job of mayor.

Bloomberg, who is leaving City Hall after 12 years, has said he plans to take a two-week vacation in Hawaii and New Zealand with his longtime girlfriend, Diana Taylor.

Then, the billionaire, who has homes in Bermuda and London, has said he will focus on his charitable foundation, Bloomberg Philanthropies, and remain active in public health, gun control and government innovation.