New York Mayor Michael Bloomberg won reelection in an unexpectedly tight race, after the media tycoon changed the city's law on term limits and spent a record amount of his own fortune to dominate the campaign.
Bloomberg had been forecast to win by double digits, but squeaked by with 51 percent against 46 percent for his Democratic challenger Bill Thompson, with nearly all votes counted.
"Everybody was shocked," a Bloomberg aide told The New York Times.
In his victory speech, Bloomberg downplayed the slim margin, saying it had been "a hard-fought victory in a very difficult year."
"Conventional wisdom says historically, third terms haven't been too successful," he said, "but we've spent the last eight years defying conventional wisdom."
Bloomberg is an independent, but ran on the Republican ballot. Thompson received almost no support from President Barack Obama's camp.
The 67-year-old mayor, who first took office in 2001, is widely credited with turning once gritty and chaotic New York into one of the cleanest, safest and most efficient US cities.
He has overseen a surge in luxury developments, barred traffic from teeming Times Square, made restaurants display calorie counts and banned smoking in bars, with a view to extending the ban to city parks.
Yet two controversies marked his path to a third four-year term in a city reeling from the Wall Street crash.
One was the astounding use of his fortune, estimated at 17.5 billion dollars by Forbes.
He burned through about a million dollars a day in the final weeks, outspending Thompson 15 to 1 with 90 million dollars in the bank. The total bill for Bloomberg's campaign was expected to exceed 100 million dollars.
Bloomberg's spending over three elections has now smashed the previous US record for self-financed political campaigns, according to the Times.
The founder of Bloomberg LP, an international news and financial data giant, had also sparked anger by strong-arming the City Council into scrapping a two-term limit approved in a referendum, thereby enabling him to run for a third time.
Exit polls showed that 45 percent of voters said Bloomberg's term limit was a factor for their vote Tuesday, and about the same proportion took his spending on the contest into consideration. He nonetheless enjoyed a nearly 70 percent job approval rating.
At a New York hotel, Thompson warned that "The work we started during this campaign doesn't end tonight, in fact, it's just beginning."
He had faced major challenges in overcoming Bloomberg's massive spending streak, raking in less than six million dollars.
Bloomberg argued in the campaign that his big business background made him uniquely suited to steer the city through troubled economic times for another four years.
New York faces deep funding shortages as a result of Wall Street cutbacks. Unemployment tops 10 percent, the municipal budget is under strain and New York State's finances are in even bigger trouble.
Thompson accused Bloomberg during the campaign of lying to the city about his intention to change the law and be allowed to seek a third term. Thompson supporters also accused Bloomberg of trying to buy the election.
Thompson gave a concession speech before a raucous hall of supporters celebrating the unexpectedly strong showing, despite his loss.
"Thank you, New York," he said, telling voters that their "desire for change is what carried me to this point."
