ATLANTIC CITY, N.J. — Superstorm Sandy slammed into the New Jersey coastline with 80 mph winds Monday night and hurled an unprecedented 13-foot surge of seawater at New York City, flooding its tunnels, subway stations and the electrical system that powers Wall Street. At least 10 U.S. deaths were blamed on the storm, which brought the presidential campaign to a halt a week before Election Day.

New York Mayor Michael Bloomberg said that the worst of the rain had passed for the city, and that the high tide that sent water sloshing into Manhattan from three sides was receding.

Still, the power was out for hundreds of thousands of New Yorkers and more than 3 million people altogether across the East, and the full extent of the storm’s damage across the region was unlikely to be known until daybreak.

In addition, heavy rain and further flooding remain major threats over the next couple of days as the slow-moving storm makes its way into Pennsylvania and up into New York State.

By late night, the center of the storm was over southern New Jersey. Just before it reached land, forecasters stripped it of hurricane status, but the distinction was purely technical, based on its shape and internal temperature. It still packed hurricane-force wind, and forecasters were careful to say it remained every bit as dangerous to the tens of millions still in its path.

“It was nerve-racking for a while, before the storm hit. Everything was rattling,” said Don Schweikert, who owns a bed-and-breakfast in Cape May, N.J., near where Sandy roared ashore. “I don’t see anything wrong, but I won’t see everything until morning.”

As the storm closed in, it smacked the boarded-up big cities of the Northeast corridor — Washington, Baltimore, Philadelphia, New York and Boston — with stinging rain and gusts of more than 85 mph. It also converged with a cold-weather system that turned it into a superstorm, a monstrous hybrid consisting not only of rain and high wind but snow in West Virginia and other mountainous areas inland.

Sandy made landfall at 8 p.m. near Atlantic City, which was already mostly under water and saw an old, 50-foot piece of its world-famous Boardwalk washed away earlier in the day.

Authorities reported a record surge 13 feet high at the Battery at the southern tip of Manhattan, from the storm and high tide combined.

In an attempt to lessen damage from saltwater to the subway system and the electrical network beneath the city’s financial district, New York City’s main utility cut power to about 6,500 customers in lower Manhattan. But a far wider swath of the city was hit with blackouts caused by flooding and transformer explosions.

The city’s transit agency said water surged into two major commuter tunnels, the Queens Midtown and the Brooklyn-Battery, and it cut power to some subway tunnels in lower Manhattan after water flowed into the stations and onto the tracks.

The subway system was shut down Sunday night, and the stock markets never opened Monday and are likely to be closed today as well.

The surge hit New York City hours after a construction crane atop a luxury high-rise collapsed in the wind and dangled precariously 74 floors above the street. Forecasters said the wind at the top the building may have been close to 95 mph.

As the storm drew near, airlines canceled more than 12,000 flights, disrupting the plans of travelers all over the world.

Storm damage was projected at $10 billion to $20 billion, meaning it could prove to be one of the costliest natural disasters in U.S. history.

Ten deaths were reported in New Jersey, New York, West Virginia, Pennsylvania and Connecticut. Some of the victims were killed by falling trees. At least one death was blamed on the storm in Canada.

President Barack Obama and Republican challenger Mitt Romney canceled their campaign appearances at the very height of the race, with just over a week to go before Election Day. The president pledged the government’s help and made a direct plea from the White House to those in the storm’s path.

“When they tell you to evacuate, you need to evacuate,” he said. “Don’t delay, don’t pause, don’t question the instructions that are being given, because this is a powerful storm.”

Sandy, which killed 69 people in the Caribbean before making its way up the Atlantic, began to hook left at midday toward the New Jersey coast.

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