Growing frustration with illegal immigration, rising public debt and an effective Internet campaign to gather voters’ signatures have put Maryland conservatives on the cusp of a victory to delay and possibly repeal a new law that would give undocumented immigrants in-state college tuition breaks.

Maryland’s version of the DREAM Act would more than halve tuition rates for undocumented immigrants at Maryland colleges and universities. For a four-year degree, the plan could cost the state $40,000 per student, and Maryland officials have estimated that hundreds of undocumented high school graduates would apply for the aid.

But a successful petition drive led by a handful of Maryland Republican lawmakers appears all but certain to stall the effort.

Opponents say they are on pace to turn in a combined 100,000 signatures by Thursday, even though state elections officials say they have certified most of the nearly 56,000 needed to suspend the law and send it to a statewide referendum in November 2012. The law had been scheduled to take effect Friday, but it has been suspended while officials await a final tally on the signatures.

“People want to enforce immigration law, not skirt around it,” said Del. Neil C. Parrott (R-Washington). “This was a highly divisive bill with bipartisan opposition that barely passed. It’s important to allow the residents of Maryland to have the final say.”

The law was approved narrowly in April by the state’s legislature and was signed into law last month by Gov. Martin O’Malley (D), making Maryland at least the 10th state to offer in-state tuition breaks to its undocumented students.

But the law appears to also be the first in Maryland that voters will decide at the polls in 20 years. The last law petitioned to a statewide referendum, which ensured abortion rights in the state, was affirmed by voters in 1992.

The signature-gathering effort to repeal the tuition law is expected to draw court challenges. But the rare success that opponents appear to be having in easily crossing the threshold for a referendum has sparked debate in Annapolis about whether Maryland’s Democratic leadership overreached in approving the measure.

In addition to Republicans, thousands of Democrats have signed on to oppose the aid for immigrants in the party’s strongholds of Baltimore and Prince George’s County.

“A referendum is extremely rare and certainly a statement of the times we are in,” said Don Norris, chairman of the public policy department at the University of Maryland-Baltimore County.

“With a bad economy and lots of people being angry, I think this is most clearly related to the economy. But we’ll see. Immigration has never been a mainstream issue in Maryland. Maybe that is changing and this will push it to the forefront.”

Michael Fix, an immigration expert at the Urban Institute in the District, said that if voters in a traditionally blue state such as Maryland repeal the law, it could affect debates in other states and possibly the debate in Congress about whether to move forward with a national DREAM Act.

“There is a lot of noise on this issue right now, and it’s hard to sum up what’s going on nationally,” Fix said, noting that the Supreme Court recently rejected an opportunity to review whether a similar law in California was legal and that lawmakers in the Senate keep pushing for a vote on a federal law.

“A repeal as a result of a referendum in Maryland would have national salience,” he said.

Kim Propeack, advocacy director for CASA of Maryland, which lobbies for immigrant rights, said that if the petition effort is successful, it will throw plans for many undocumented immigrants who graduated from Maryland high schools this spring into limbo and leave college out of reach for many financially.

Under the law, students who can prove that they have attended Maryland high schools for at least three years and that their parents or guardians have begun paying taxes would be allowed to begin courses this fall at community colleges at in-state rates.

Those who go on to earn an associate’s degree could transfer to a four-year institution at in-state rates. At the University of Maryland, tuition was $8,415 for in-state students, compared with $24,830 for out-of-state students.

Propeack said that legal challenges to the referendum effort are likely and predicted that voters would ultimately see the many benefits of the law.

“We look forward to refocusing the issue not on the number of signatures and petitions, but on the benefits to so many of Maryland’s kids,” she said.

Legal challenges are expected to focus in part on a new online tool opponents built and used to secure tens of thousands of signatures.

In preparation for a possible referendum effort against same-sex marriage legislation that died this year in Maryland, Parrott paid about $2,500 of his own money to build a tool that has eliminated many clerical errors that routinely doom signature-gathering drives in Maryland.

Because signatures can be rejected if they do not match voter rolls, the online tool prints out a Maryland voter’s name and information exactly as it is listed in registration records. A voter only needs to sign the petition as printed and mail it to the campaign.

More than a third of the 47,288 signatures validated for the referendum have come from the online tool, according to the State Board of Elections.

Last month, the American Civil Liberties Union of Maryland wrote a letter asking the elections board to scrutinize the tool.

It could not only “determine the fate of the DREAM Act petition effort,” the letter read, “but could also dramatically change the petition process in Maryland going forward, opening many more state and local laws to petition challenges in the future.”

Hopefully that’s the case, said Parrott, who has recouped his $2,500 in donations from opponents of the tuition law.

“There’s always a question of how can we make it easier for people to get involved in the process. This computer program does that well, so get involved.”