ALBANY – When the New York City schools chancellor, Joel Klein, arrived in Albany last Tuesday morning to argue that lawmakers should lift a cap on the number of charter schools allowed in the city, he was greeted by a somewhat unlikely group of legislative allies.

A mix of Republicans and Democrats, the sympathetic members of the Senate and the Assembly were all from urban areas. Their support for charter schools, or independent public schools, suggests that on this issue more than most, allegiances are not forming strictly along party lines.

Charter schools were a top priority for Governor Pataki during the early years of his administration, with the Republican governor arguing that public schools would improve if they were forced to compete with independent schools. Mr. Pataki convinced legislators to go along with the plan in exchange for a raise, reaching a deal in 1998 that allowed for the creation of 100 charter schools statewide.

New York City has already established roughly half of the 80 charter schools that currently operate in the state and is seeking permission to have the cap lifted within the five boroughs. Yet with 16 additional charter schools pending across the state, a Republican from Brooklyn, Senator Martin Golden, looking to go beyond Mr. Klein’s request, introduced legislation to lift the cap statewide.

During his visit to Albany, Mr. Klein pressed lawmakers to get behind Mr. Golden’s bill but said removing the cap in the city is “our focus.”

Mr. Golden’s bill is likely to die in the Republican-led Senate despite Mr. Klein’s support and that of several Democrats. He told The New York Sun he has fewer than 20 colleagues from either party in the 62-member chamber lined up to back the proposal. The reason for the tepid support is not clear, though the group that greeted Mr. Klein suggests that constituent pressure is in tension with organizations that oppose charter schools.

By siding with parents against those opponents, Democrats in the Assembly and the Senate are taking a calculated risk against the politically powerful teachers unions. Republican legislators, most of them from upstate, are not under the same pressure to improve schools as are their downstate colleagues. They can vote against charter school expansion without fearing a backlash from constituents.

In addition to Mr. Golden, the group that greeted Mr. Klein included two Manhattan Democrats, Assemblyman Adriano Espaillat and Senator Malcolm Smith; a Queens Democratic senator, Toby Ann Stavisky, and two Brooklyn Democrats in the Assembly, Roger Green and Joan Millman.

Advocates of charter schools said the growing number of Democrats who support charter schools suggests the issue will become increasingly controversial in coming years. They said constituents in urban areas are forcing lawmakers to present more options and could rebel once the cap is reached.

“There’s going to be more charter applicants than available charters by this fall, which means that by the time legislators return next year, there will be a backlog of angry applicants and angry parents,” the executive director of the New York Charter Schools Association, Bill Phillips, said. “I think they’re going to hear that from the parents. You’ve already got legislators on both sides saying I want these in my district.”

The United Federation of Teachers, the New York City teachers’ union, has itself applied to open two charter schools. The union has been reluctant, however, to put its support behind the movement. Senator Smith, who helped establish two charter schools in his district, said union organizing could help explain why constituent pressure has not compelled more legislators – Republican and Democratic – to line up behind a law that would lift the cap.

A recent report on political action committees, or organizations that funnel money to political campaigns, shows that New York State United Teachers, the state’s largest union, gave almost twice as much money to state legislative candidates last year through its political action committee than the second-largest PAC. The report, by the New York State Public Interest Research Group, found that the teachers’ union gave the candidates a total of $1.3 million.