Lawmakers in Albany were given a powerful reminder of the political danger of siding in favor of school choice measures when the state’s largest teachers union yesterday endorsed the Republican candidate in an important special election that will take place next month for a seat in the state Senate.

For New York State United Teachers, which represents nearly 600,000 teachers, custodians, bus drivers, and clerical employees, its preference came down to a single factor.

The Democratic candidate for the Senate seat, Assemblyman Darrel Aubertine, had attached his name to legislation that would give tuition tax credits and other benefits to parents of children in private and parochial schools. The Republican in the race, Assemblyman Will Barclay, had not. Control of the state Senate in New York is in the hands of a narrow Republican majority that Governor Spitzer, a Democrat, has expressed hope of dislodging.

Mr. Spitzer left a tuition tax deduction out of his proposed budget this month after earlier promising religious school leaders that he would include it. The decision by Mr. Spitzer drew an unusual public rebuke from the archbishop of New York, Edward Cardinal Egan, and four prominent Orthodox rabbis. Last night, in his State of the Union address, President Bush proposed federal scholarships for poor students to attend private and parochial schools.

“This is a big issue for us, quite frankly,” the president of the New York State United Teachers, Richard Iannuzzi, said in an interview. While the union considered Mr. Aubertine a friend, his record on the private and parochial school funds question is a “diversion that concerns us,” Mr. Iannuzzi said.

The rejection of Mr. Aubertine, on whom Mr. Spitzer and state Democrats are counting to take over an open Senate seat in northern New York, is a vivid example of the consequences confronting lawmakers who don’t toe the line set by Albany’s major interest groups, which keep a vigilant eye on voting and sponsorship records.

“What message does it send if you ask people to support you on that issue and then you endorse somebody who hasn’t supported you?” Mr. Iannuzzi said. “We would be sending a mixed message. The issue here is that we look at records.

NYSUT is one of the Senate Republicans’ largest contributors. Between January 1, 2005, and December 31, 2007, the union contributed $654,831 to members of the Senate Republican conference, with each member receiving at least one check, according to the New York Public Interest Research Group.

In 2006, Mr. Aubertine was among several co-sponsors of a two-house bill that would have provided lower-income parents of children in private or public schools a refundable tax credit of up to $3,500 to offset the costs of tuition, tutoring, textbooks, or academic summer camp.
The union considers tax credits as a “precursor” to tuition vouchers and warns they would divert money from public school districts and thus teachers.

The bill never came close to passing. That year, Governor Pataki sought to insert a $1,000 tax credit in his budget, a measure the legislature also blocked.

Mr. Iannuzzi said the teachers union would be setting up a phone bank operation to call the 10,000 members with the district and urge them to vote for Mr. Barclay, the Republican. The union also plans on mailing endorsement pamphlets to its members and promoting the assemblyman in its in-house newspaper.

A spokesman for Mr. Aubertine said the candidate was perplexed by NYSUT’s support of his opponent and noted that the Democratic assemblyman has won the backing of steelworkers and other local unions in the district, which includes Oswego and Jefferson counties.
Mr. Barclay did not return calls for comment.

While succeeding in expanding the number of charter schools, school choice advocates in recent years have largely failed in their effort to persuade Albany lawmakers to give parents private school tuition breaks, whether in the form of a tax credit or deduction.

Last year, Mr. Spitzer sought to insert into the budget a measure that would give parents tuition tax deductions of up to $1,000 — said to be worth about $65. The speaker of the Assembly, Sheldon Silver, vigorously opposed the proposal, which disappeared from the final budget agreement.

Mr. Iannuzzi said the Republican majority leader of the Senate, Joseph Bruno, and other Republicans have typically sided with the union on the issue of private school tuition tax benefits.

“At the end of the day, we have not had concern that the Senate majority would oppose us on our feelings in general on the whole approach to vouchers and tax credits,” he said.

Triggered by the retirement of the Republican incumbent, James Wright, the special election between Mr. Aubertine, a former dairy farmer, and Mr. Barclay, a partner of the law firm of Hiscock and Barclay and the son of a former state senator, is a must-win for Mr. Bruno’s conference.

A loss on February 26 would deprive Republicans, who are hanging onto their majority by two seats, of any cushion to protect their conference against a sudden retirement, or a decision by one of their members to switch parties or caucus with Democrats.

Mr. Spitzer, whose aggressive efforts to bring Democrats to power in the Senate has been a source of enormous friction between his administration and Republicans, has deployed his political team to oversee the race.

To win, Mr. Aubertine will have to draw support from a large number of Republicans, who outnumber Democrats by a 30,000 margin in a district with about 135,000 registered voters.