As Gov. George E. Pataki picked up the endorsement of the teachers' union in Yonkers — and with the New York City teachers' union expected to follow suit imminently — H. Carl McCall joined several educators yesterday to denounce the governor's education record.

Mr. McCall, the state comptroller and Democratic candidate for governor who has sought to make education one of his signature issues, appeared outside the O. Henry School at 333 West 17th Street, in an attempt to stop the governor's momentum on the issue. Mr. McCall's supporters praised him for his stands on education and criticized Mr. Pataki for what they considered his insufficient financing of it. They also suggested Mr. Pataki's union backing, particularly among teachers, was not deep.

"Politically, it's a miscalculation," said Michael Krasner, a professor at Queens College. "I think you're going to see rank-and-file teachers breaking rank with the leadership."

The expected endorsement by the city's teachers' union would be the latest in a series by unions that have traditionally supported Democrats. Mr. McCall has characterized the support as paybacks for handouts from the governor.

In Yonkers, Steve Frey, the president of the Yonkers Federation of Teachers, in announcing the union's backing, noted Mr. Pataki's financial bailouts of the school district, including $5.5 million designated in August to avert the layoff of 158 teachers.

The Yonkers teachers' union was the first affiliate of the state union, which is staying neutral in the race, to endorse the governor, his campaign aides said.

Mr. McCall and his supporters have repeatedly said that union members would not follow the recommendations of their leaders. But on Monday, members of the 55,000-member Public Employees Federation voted down a resolution to overturn the executive committee's endorsement of Mr. Pataki.

Union officials had said they decided to endorse the governor after he promised to restore three lost sick days to union members. Yesterday, the sponsors of the resolution and the union president said that members feared that switching to Mr. McCall would compromise the union's credibility. "Hundreds of people who were wearing McCall stickers voted not to overturn the endorsement," said Dan Steen, one of the resolution's sponsors.

Roger Benson, the public employees union president, issued a statement saying that members "understood that switching our endorsement would have eroded our ability to protect and enhance our members' rights and benefits."

Asked if he would call for an investigation into whether union votes were exchanged for favors, Mr. McCall said yesterday, "Maybe we should do that."

After his news conference in Yonkers, Mr. Pataki headed for Midtown Manhattan to announce that the state had acquired the two-block, 1.4- million-square-foot James A. Farley Building, which will be converted from a post office into a new Pennsylvania Station.

The state paid $230 million, using funds from the Port Authority of New York and New Jersey and the city of New York and $85 million in bonds from the Empire State Development Corporation, which expects to recoup its costs through revenues from the retail and commercial parts of the new station.

State officials and the Postal Service signed a memorandum of understanding yesterday, with a final sale expected within the next year, said Charles A. Gargano, chairman of the development corporation.

Mr. Pataki, standing with Mayor Michael R. Bloomberg, former Senator Daniel Patrick Moynihan, who championed the station project, and Rudy Umscheid, vice president of facilities for the post office, called the new station "a world-class, 21st-century landmark gateway to New York."

The economic development announcement was another of a series being made by the governor ahead of the Nov. 5 election, in which he is seeking a third term.

Meanwhile, Mr. Pataki was criticized yesterday for his handling of the state budget by the Manhattan Institute, a conservative organization that has in the past supported his fiscal policies. The institute released a report saying Mr. Pataki would have to return to the hard-nosed, budget-slashing tactics of his first term to weather an estimated $5 billion shortfall next year.

The report, by E. J. McMahon, an institute analyst, said Mr. Pataki had reined in spending in his first four years in office, but had let it increase at twice the rate of inflation in his second term.

Mr. McMahon also said the governor this year spent the $3 billion cushion he had saved in the late 1990's to avoid having to make cuts before an election. To close next year's gap, Mr. McMahon predicted the administration would have to cut 20,000 jobs, freeze state employee salaries in the next round of contracts, stop the growth of Medicaid and sell off some state assets like golf courses and hospitals.

Mr. Pataki said he had not yet read the report and would not comment on it. Asked about the looming budget crisis, he said: "We've gotten through this year, and we're going to do fine next year as well. We are well prepared."