ALBANY – With just a month left before lawmakers leave Albany and head home to campaign for re-election, charter school advocates are dramatically increasing pressure on the Assembly speaker to lift the statewide cap on the independently run schools.

Charter schools supporters told The New York Sun that they plan to spend at least $1 million on a television and radio advertising campaign targeting Democrats who are resisting their efforts. They have also hired one of Albany’s highest-paid lobbyists, Brian Meara, who is well known around the state capital for his close ties to the speaker, Sheldon Silver.

“We talked with a bunch of people and tried to figure out who were the effective lobbyists who worked in Albany. His name came up and up,” said Amy Wilkins, the executive director of the Washington-based Education Reform Now-Advocacy Committee, which is about six months old.

The group has ties to Democrats for Education Reform, a political action committee that collects money for Democratic politicians who support school choice issues. Ms.Wilkins serves as the treasurer of the group. Mr. Meara has represented the nursing and adult home industry, the New York Yankees, and NYC2012, the organization that supported New York City’s failed Olympic bid.

The expansion of charter schools is emerging as one of two key wedge issues dominating debates here as the legislative session winds down and the atmosphere becomes ripe for dealmaking after a relatively unproductive legislative session.

Republicans who control the state Senate are also pressuring Mr. Silver’s Assembly Democrats to pass anti-crime legislation that has sharply divided both houses and created gridlock.

As usual, Mr. Silver holds the cards on both issues because of his willingness to drag out negotiations. Republicans are in jeopardy of losing their control over the Senate and are eager to expand the state’s criminal DNA database and eliminate the statute of limitations for sex crimes before they head home to voters.

The criminal justice matters are taking a backseat this week to charter schools. Democrats spent Monday and yesterday in closed-door discussions about how to handle the issue, and more private talks were planned for today. The concept of adding more charter schools has considerable backing among members of the influential black and Puerto Rican caucus.

Charter school advocates say they support Governor Pataki’s plan, proposed in January in his executive budget, to increase the maximum number of charter schools to 250 from the current cap of 100 and exclude New York City from limits.

The governor also wanted to grant the city the power to authorize 50 schools. Lawmakers threw out the proposals, as Senate Republicans argued that the expansion issue ought to be dealt with after the completion of the budget.

New York has 79 active charter schools, which enroll about 22,500 students, according to the New York Charter Schools Association in Albany. Twenty-one more schools are slated to open in the fall.

Few issues dominate so much time and the drawn-out discussions indicate the volatile nature of the debate. Charter school advocates say the schools, which are public but independent of school boards, are more tailored to the needs of students and more accountable because their charter renewal often depends on student performance. Opponents say there’s little proof showing that charter students are better served, and they fear the schools drain money and resources away from school districts.

On Friday, the leader of the city’s teacher union, Randi Weingarten, held a rare meeting with charter school supporters, including the president of the New York Charter Schools Association, Bill Phillips.

Both Mr. Phillips and a spokesman for Ms.Weingarten declined to provide details about the meeting, which was held at the union’s headquarters.

Ms.Weingarten, whose union recently opened its own charter elementary school, is eager to see more of the schools unionized. An entry on the official Web log of the United Federation of Teachers, Edwize.org, said the purpose of the meeting was “to see if we could find common ground, consistent with the core principles of both sides, which would allow us to move the New York charter school movement forward in a positive direction.”

Mr. Phillips is affiliated with Parents for Public Charter Schools, a 501(c)(4) advocacy organization that is aiming to raise more than $2 million for the ad campaign. That amount makes the effort one of the largest issue-driven campaigns in New York in recent years.

On Saturday, the group unveiled a radio spot airing in Albany that features a mother praising charter schools and attacking a Democratic lawmaker, Ronald Canestrari, who represents part of Albany.

“I’m a mom, and nothing is more important to me than my children,” the mother says. “That’s why I enrolled my son and daughter at a public charter school. The school is safe, small, and high quality.That’s why I am so mad to know that Assemblyman Ron Canestrari is ‘dead set’ against letting any more parents choose public charter schools for their children.”

Mr. Phillips said the group received money from individuals but would not provide their names.