Organizers of an effort to repeal a Maryland law granting college tuition breaks to illegal immigrants said Tuesday that they are well ahead of pace in collecting enough signatures to force a public vote on the issue.

The law, signed this month by Gov. Martin O’Malley (D), would allow illegal-immigrant students to pay the lower in-state rates at the state’s colleges and universities. To be eligible, students must have attended a Maryland high school for three years, provide proof that their parents are taxpayers and express their intent to become a citizen.

Opponents of the new law have until June 30 to collect the 55,736 signatures — or 3 percent of the number of votes cast in the last gubernatorial election — required to hold a statewide referendum on the law.

Tuesday marked a deadline for opponents to present one-third of that number to the state, or 18,579. Leaders of the group said they are prepared to turn in more than 40,000 by 9 p.m. Tuesday.

“People are clamoring to sign this petition,” said Del. Neil C. Parrott (R-Washington), chairman of the group. “In Maryland, we’re going to send a message to the whole United States.”

In past petition drives, a large percentage of signatures have been thrown out because they do not match the names of voters as they appear on the state’s voting rolls.

Parrott, who appeared with four other Republican delegates in the back parking lot of the State Board of Elections in Annapolis, said his group is taking particular care to turn in only valid signatures.

The law is slated to take effect in July, allowing students to qualify for in-state tuition rates at community colleges starting in the fall. But if opponents collect enough valid signatures, the law would be put on hold until the next general election, in November 2012.