“Some places manage their way into fiscal problems, and other places are beset by social forces, many of them outside of their own control,” said Steven J. Hancox, a deputy state comptroller who oversees local government. “Nassau has had a history where the populace has enjoyed a variety of services, and those cost money.

“It doesn’t really matter where you are; when the money dries up you have tough choices to make.”

While voting 6 to 0 to take over the county’s finances, the control board, the Nassau Interim Finance Authority, stopped short, for now, of declaring a financial emergency, which would also allow it to impose a wage freeze on county workers. But it said that remained a likelihood if Nassau’s leaders did not comply with its demands to cooperate in bringing the county’s spending into line with revenues by Feb. 15.

“The taxpayers elected a team,” the authority’s chairman, Ronald A. Stack, said. “Hopefully the team will be able to perform.”

Yet the takeover was a stinging rebuke to Nassau’s county executive, Edward P. Mangano, a Republican who took office a year ago after upsetting a popular incumbent in 2009. Mr. Mangano had repeatedly said the budget was balanced, and then insisted there were ample contingencies to cover any shortfalls. But the authority said that many of his assertions were unfounded or unsupportable.

Should the county choose to work closely with the authority, it could seek to reopen talks with labor unions, emboldened and newly empowered by that alliance. But the response from the county on Wednesday was adversarial in tone.

“Who elected them?” asked the county attorney, John Ciampoli, referring to the authority.

Mr. Mangano, speaking to reporters after the board’s decision, said he was considering a lawsuit to block the takeover, accused the authority of wanting to raise property taxes and urged taxpayers to question its “motivation.” He has accused the board members of having partisan Democratic sympathies.

Mr. Stack, a veteran municipal banker who as a state official was involved in addressing the 1975 New York City fiscal crisis, said the county’s deficit, under the strict accounting standards required by state law, was $176 million, or more than six times the threshold of 1 percent of the budget  above which the law required the authority to take control.