There are budget tricks, and there are budget tricks.

Some governors go to enormous lengths and expense to improve the way their finances look. They sell highways or government buildings, delay worker paychecks or tax refunds, or concoct new and costly ways to borrow money.

This year, Gov. Andrew M. Cuomo is pulling a budget trick … on a budget.

“We have gone from a $10 billion deficit to a $2 billion surplus in just three short years,” Mr. Cuomo, a Democrat seeking re-election in November, declared in his State of the State address this month.

Left unexplained was the source of that surplus.

Mr. Cuomo’s official financial plan shed a little light, but not much: A four-sentence footnote essentially says that the surplus will materialize if the governor persuades lawmakers to approve big cuts to planned increases in spending in future budgets. The “magic footnote,” as one analyst christened it, thus contains a multibillion-dollar caveat.

That has not stopped Mr. Cuomo from trumpeting the $2 billion surplus as a leading success of his time as governor — as if he had already achieved it. But New Yorkers will also have to wait awhile to see if the governor’s confidence proves warranted.

While the state expects some extra money as early as this year, he did not point out in his speech that a $2 billion surplus would not come, if it comes at all, until the 2016-17 fiscal year.

The budget for that year would be negotiated two years from now, well into his second term. Hypothetically.

“The $2 billion surplus is strictly notional,” said E. J. McMahon, president of the Empire Center for Public Policy, a conservative research group. “That’s a fine goal. But you can’t claim credit politically for having a good goal.”

To achieve it, the footnote explains, Mr. Cuomo and the lawmakers who approve the budget in future years will need to hold increases in state spending to no more than 2 percent annually.

Those lawmakers have not been elected yet.

In the governor’s defense, his first three budgets did manage to keep state spending growth below 2 percent — no easy feat, given that education andMedicaid spending have risen around twice that amount.

Matt Wing, a spokesman for the governor, said critics were unwise to doubt that Mr. Cuomo could continue enacting equally austere budgets.

“All budgets make assumptions,” Mr. Wing said. “We are assuming that the state does the same thing it has done for the past three years, while this claim assumes the state does something radically different. Which theory is more probable?”

Undeterred by the perils of prognostication, Mr. Cuomo has already decided what to do with his hoped-for future windfall: He is counting on it to pay for tax cuts he has proposed.

Elizabeth Lynam, director of state studies for the Citizens Budget Commission, said Mr. Cuomo’s track record was compelling, but finding billions in savings is never easy.

“He’s saying, ‘Trust me,’ ” she said.