Opponents of a new law to extend in-state tuition discounts to illegal immigrants delivered nearly 75,000 more signatures to the state Thursday, a number they believe is more than enough to keep the measure off the books until voters have their say.

After submitting more than 47,000 valid signatures last month, they needed fewer than 8,500 more to be certified by the State Board of Elections to get the law onto the 2012 ballot.

If they are successful, it would be the 18th time in Maryland history that a law approved by the General Assembly was sent to voters for reconsideration.

Volunteers carried boxes of petitions into the office of the secretary of state in Annapolis shortly before 9 p.m. The deadline was midnight.

Del. Neil Parrott, the Washington County Republican who has led the petition drive, expressed confidence. "We can't break the rules for some people," he said. "We are a nation of laws."

When Parrott announced the drive two months ago, even opponents of the law were skeptical of the chances of success, given the state's strict rules for petitions.

But the effort was boosted by the organizers' sophisticated use of the Internet, simmering frustration over the economy and a deep mistrust among some over how the Democratic-controlled General Assembly spends taxpayer dollars.

Del. Patrick McDonough said the petition drive was the "most successful" ever launched in Maryland. Looking toward November 2012, he declared: "We are now in campaign mode."

The law, which was supposed to go into effect Friday, would allow illegal immigrants to attend public colleges and universities in Maryland at the same in-state tuition rates paid by legal state residents. It is projected to cost taxpayers $3.5 million annually by 2016, according to a legislative analysis.

Though the signatures will almost certainly be challenged in court, supporters of the new law conceded that the referendum is likely. Immigration activists and clergy launched a counteroffensive yesterday, kicking off a public relations campaign aimed at refocusing the debate on compassion.

"My tradition takes seriously the obligation to welcome all of God's children," the Rt. Rev. Eugene Taylor Sutton, bishop of the Episcopal Diocese of Maryland, said at a rally Thursday morning in Baltimore. "We are talking about 'our children,' not 'those children.'"

The religious leaders pledged to mobilize their members in support of the law.

"If this goes to referendum, get out of our way," said Bishop Douglas I. Miles, pastor of Koinonia Baptist Church in Northeast Baltimore. "All of us will be out in the streets campaigning for the Maryland Dream Act."

Illegal immigrants also attended, clapping occasionally and holding up purple-and-yellow signs that read "Defending the Dream."

For Karen, a 16-year-old rising senior at Annapolis High School, qualifying for in-state tuition could save her family between $4,000 and $6,000 per year at a community college, and as much as $17,000 at a four-year college, according to a legislative analysis.

To get the break, an illegal immigrant would have to attend high school in Maryland for at least three years and show that his or her family had filed state tax returns.

Following graduation from high school, the student could attend a community college at the in-state rate. Under the law, the student would have to complete 60 credits at a community college — the equivalent of two years of full-time study — to become eligible for the residential discount at a four-year college.

"We worked so hard to get this to pass," said Karen, who agreed to talk only on the condition that her last name was not used because she and her family are not in the country legally. "We just want an education."

The opponents have been working hard, too. They fanned out across the state in the last three months, knocking on doors, setting up tables in public spaces and directing voters to a website that made signing easy in the effort to collect the 55,736 valid signatures they need to get the law on the ballot. Parrott said that $7,500 was spent on the petition effort.