As more charter schools open in New York City, the odds of getting into the privately managed public schools are rising while the demand for seats continues also to rise, according to the New York City Charter School Center.

James Merriman, the center's CEO, said it's getting "marginally easier" for children to get into charter schools. About 27 percent of applicants get in, compared to 20 percent two years ago. Still, he added, there were 50,400 students on the waiting list for a total of 18,600 seats this year,

Charter schools are required to accept all students who apply; they hold lotteries when they get more applications than seats. The center surveyed the city's 183 charter schools about their lottery application rates; 85 percent of them responded. Based on this data, the center determined that a total of 181,600 separate applications were made from 69,000 individual applicants. Many students apply to more than one charter.

"Even though we're adding 18,600 seats that are available this year for incoming children, unfortunately because of the demand we still end up with over 50,000 students on the waiting lists," Merriman said. So parents continue to choose charters and we see this trend year after year after year."

The charter center's annual waiting list report comes during an election year when supporters and opponents of charter schools are trying to influence the candidates for mayor. It follows the release of the charter center's advertising campaign promoting the success of its schools. Merriman said four different ads were made, and that his center is spending "in the six figures" to run them on basic cable.

But critics of the privately run public schools have long complained that charters siphon resources from the rest of the system, creating new opportunities for a small percentage of children without helping the vast majority of those in regular district schools. Many parents and teachers also bristle when charters open inside the same buildings as district schools, requiring the different schools to share libraries, cafeterias and hallways.

There are also some who believe charters deliberately "dump" low performing students, a claim Schoolbook was not able to definitively prove.

Schoolbook made an interactive map of charters last fall.

Over the weekend, five of the Democrats running for mayor and one independent candidate appeared at a forum held by the teachers union. All of the candidates except for City Council Speaker Christine Quinn said they would support a moratorium on placing several schools in one building. Quinn said she might allow for it in “some cases.”

A teacher from Washington Irving high school, which is being phased out, asked the candidates point-blank what they thought about former Councilwoman Eva Moskowitz, whose Success Academy charter network has caused more friction than most because it has so many charters now inside district schools.

Quinn said she supported teachers union president Michael Mulgrew's call for a "truth commission" that can look into "how decisions get made about what schools are going to what buildings, so we're not all scratching our heads at times about how these things occur."

Public Advocate Bill de Blasio said it was "time for Eva Moskowitz to stop having the run of the place. She has to stop being tolerated, enabled, supported."

In an email to The New York Times, Moskowitz responded to the charges with this: “The mayoral candidates are desperate for a U.F.T. endorsement."

On Monday, Mayor Michael Bloomberg was asked whether he thought unions would have an "undue influence" in the next mayoralty.

"If the next mayor wants to take the city back to where it was 11 years ago when the teachers ran the school system," he said. "When books couldn't be delivered, when teachers weren't paid, when they weren't hired, when minority kids were hopelessly behind white and Asian kids, where there was no accountability, where crime is rampant in the schools, God help us."