The group has joined in a public relations campaign that kicked off last week to shift the focus to civility and blunt the economic criticism by arguing that the law should be viewed as an investment in the state's youth.
Other supporters of the breaks held out optimism that the referendum could be shut down.
David Rocah, an attorney with the American Civil Liberties Union of Maryland, pointed to a petition drive that appeared to have been successful in 2001, only to be exposed as fraudulent during a court challenge. "The fact that the board has validated the signatures does not mean that the signatures are in fact valid," Rocah said.
The last time a law was put to the voters was in 1992, when a group successfully petitioned a law affirming a woman's right to an abortion to referendum. Voters upheld the law.
This time the ACLU has raised questions about whether the petitions generated through Parrott's website pass legal muster.
Casa de Maryland, which also supported the law, is preparing a court challenge. The group has requested copies of all 132,147 petitions and expects that many will be disqualified.
"I obviously was not expecting them to [reach the goal] today," said Kim Propeack, a spokeswoman for the group.
Should the court efforts fail, Propeack said, she's "looking forward" to discussing the issue during a statewide campaign. She expects CASA to be joined by "national partners" backing their efforts.
On the other side, national groups are already watching. A spokesman for the Federation for American Immigration Reform, a Washington organization that opposes extending benefits to illegal immigrants, said Thursday that they would support the repeal "in any way that we can."
Spokesman Ira Mehlman cited California and Arizona as states where laws that supported illegal immigrants were beaten back at the ballot box, and predicted Maryland would be no different.
"It is simply unjustified to be granting new benefits to illegal aliens at a time when the state is cutting service to everyone else," he said.
The local boards of elections have until July 20 to finish counting signatures. The list must be certified by July 22.
Sen. Victor Ramirez, the Prince George's County Democrat who sponsored the bill, said he expects "the people of Maryland to get on board" when a campaign in support of the law is launched.
"If you are paying income taxes in the state of Maryland," he asked, "why shouldn't you pay the in-state rate?"