Budget-watchers skeptical of the administration's numbers say the shortfall might actually be greater, citing several factors, including Internet gaming revenue. The administration projected it would take in $160 million from online gambling during the fiscal year that began July 1. Internet gaming became legal in November; through January, it has netted the state $2.68 million.
Because the state constitution requires that budgets be balanced, Christie will have to account for any shortfall within this year's budget, which ends June 30.
A fix may not be easy. Last year, Christie delayed about $400 million in property-tax rebates.
Kevin Roberts, a Christie spokesman, declined to comment on the shortfall and what approaches the administration might take to close it. "The governor will address these issues of revenue and expenses in his budget address to the Legislature on Feb. 25," Roberts said.
The annual budget speech comes as Christie remains under investigation for his administration's role in the September lane closures at the George Washington Bridge and amid criticism of the distribution of Sandy aid.
Lawmakers will be paying close attention to what the governor proposes.
"The first move is his," said John Burzichelli (D., Gloucester), vice chair of the Assembly Budget Committee.
Of particular concern in the budget will be the increase in the state's pension obligation - projected to rise to more than $2 billion next year.
"That's a hard, bright-line additional expense that's going to be incurred," Burzichelli said. "I don't know that we've had revenue growth to strictly cover that."
Revenue estimates have been a source of contention between Christie's administration and the Office of Legislative Services. Last May, the nonpartisan office's budget and finance officer, David Rosen, told lawmakers that revenue would fall short of Christie's projections by $937 million.
At the time, Christie dismissed Rosen's estimates as "dead wrong."
"I don't know, candidly, whether he's just lost it or just playing politics," said Christie, who has called Rosen "the Dr. Kevorkian of the numbers."
The shortfall currently facing the budget doesn't mean state revenues aren't growing. They are - by 5.7 percent through the first six months of the fiscal year.
But Christie had budgeted based on more aggressive revenue growth.
Joseph Seneca, a professor of economics at Rutgers University and former chairman of the New Jersey Council of Economic Advisers, said the still-undisclosed January revenues would be significant, accounting for some holiday spending and Jan. 15 estimated tax payments.
Treasury officials typically release the numbers midmonth. Asked Friday when the January figures would be available, a spokesman provided the same statement Roberts had issued, indicating they may not be available until the budget speech.
The stock market has been strong, Seneca said, which could translate into better tax revenues for the state.
"All that's to say is, you've still got half a year," Seneca said.
In the second half of the year, the state has less spending available to adjust the budget and offset the shortfall, said David Rousseau, who was deputy state treasurer and treasurer under Democratic Govs. James McGreevey and Jon Corzine.
Now a budget and tax analyst for New Jersey Policy Perspective, a liberal-leaning think tank, Rousseau said governors tend to favor higher revenue estimates: "It's easier for an administration to generally lean toward the high range and just hope."
While lawmakers could choose a lower revenue estimate, "then they have to cut," Rousseau said. "Legislators don't like to cut."
Rousseau projects that by the fiscal year's end, the shortfall will be between $540 million and $1.16 billion, including estimates for unexpected Internet gaming revenue and figures included in a bond prospectus that Rousseau said indicate last year's closing surplus may be smaller than budgeted.
The bulk of the revenue shortfall can be attributed to slower than expected growth in the income tax and corporate business tax - "notoriously a very difficult revenue to forecast," Seneca said. Corporations "can move things from quarter to quarter" between federal and state taxes, he said.
Income tax revenue, meanwhile, was unusually large in December 2012, when some higher earners took capital-gains income early to avert higher federal tax rates that went into effect at the start of 2013.
As a result, comparing growth this December to the year prior is tricky, Seneca said.
Forecasting revenue is "a moving target," he said. "It's not a fine science of precision."
While revenues are growing, the state's economic picture is mixed, experts said.
New Jersey added 34,000 private-sector jobs in the first half of 2013, ranking eighth in the country, said James W. Hughes, dean of the Edward J. Bloustein School of Planning and Public Policy at Rutgers.
"And then somebody hit the pause button and we started losing jobs in the second half of the year," he said. "It's sort of inexplicable right now."
While cautioning that revised economic indicators would be available in March, Hughes suggested that the slow rebuilding effort after Hurricane Sandy was partly to blame: "Even though it was technically open for business, the Shore season was a disaster. We exported dollars to Maryland, Virginia, Delaware beaches and the like."
But Hughes said New Jersey's economic woes were not unique. "The Northeastern states generally are lagging, have been lagging the nation," he said, with more jobs going to states such as Florida and North Carolina, where housing and other cost-of-living expenses are lower.
Staff writer Andrew Seidman contributed to this article.