Gov. Martin O'Malley signed into law the death penalty repeal, making Maryland the 18th state to abolish capital punishment. (Barbara Haddock Taylor/Baltimore Sun video)

One day after Gov. Martin O'Malley signed legislation to abolish capital punishment in Maryland, death penalty supporters said Friday they will launch a petition drive to give voters the opportunity to overturn the new law.

At a news conference, Baltimore County State's Attorney Scott Shellenberger said he plans to lead the effort to "repeal the repeal" of the state's death penalty.

"We need to retain the death penalty for those prosecutors who wish to seek it because it is simply the right thing to do for public safety," said Shellenberger, a Democrat. "We want the people of Maryland to decide whether Maryland should have the death penalty."

Del. Neil Parrott, a Western Maryland Republican, said he would mobilize his signature-gathering operation, MDPetitions.com, to try to put a death penalty question on the ballot in November 2014.

The effort raises the prospect of another hard-fought referendum campaign next year after Maryland voters had the final say on several ballot questions in 2012.

If the signature-gathering process is successful — as many expect it will be — voters will decide an emotional issue on which polls show they are closely divided.

Supporters of repealing the death penalty say they are prepared to defend the new law, which was a priority of O'Malley's.

"We are disappointed that the great achievement toward justice we achieved in recent weeks has been challenged, but we are prepared to defeat it," said NAACP President Benjamin Jealous. "If this goes to referendum, the NAACP and countless allies throughout Maryland will be there to fight."

The General Assembly voted this year to erase capital punishment from Maryland's law books after more than 300 years. If the referendum challenge fails, Maryland will become the 18th state to repeal its death penalty.

Parrott said the death penalty repeal measure is the only statewide legislation from this year's General Assembly session that his group would attempt to petition to referendum.

He said MDPetitions.com, which uses the Internet to streamline the process of gathering signatures, wants to focus its efforts on a single issue. That means some other legislation that had been under consideration for petition drives, including one allowing people who are in the country illegally to obtain driver's licenses, will go unchallenged unless another group steps up to mount a campaign.

Parrott previously said he would not gather petitions to challenge O'Malley's sweeping gun control bill, though the group Free State Petitions has said it will.

Parrott's reluctance to take on too many causes reflects MDPetition.com's experience in 2012. For that election, the group was successful in helping to petition three laws to referendum — measures legalizing same-sex marriage, setting new congressional redistricting lines and allowing some people in the country illegally to pay in-state tuition at Maryland colleges.

Voters upheld all three laws, prompting complaints in Republican circles that neither the party nor Parrott's group were prepared to mount a campaign once a question was on the ballot.

Shellenberger said the 2012 election showed that opponents of a law can't lose their focus once they collect enough signatures to put a question on the ballot.

The death penalty bill cleared both houses of the General Assembly with votes to spare. But Shellenberger said he expects the emergence of a grass-roots campaign to reinstate it, including efforts by state's attorneys and unions representing police and correctional officers.

To succeed, opponents of repeal will have to gather 55,736 valid signatures by June 30 — the first third of them by May 31.

Maryland's Roman Catholic Church, which supplied much of the lobbying clout behind repeal, said Friday that is urging its members not to sign the petitions.

"For the Catholic Church, repeal of the death penalty is an integral part of our pro-life efforts to uphold the sanctity of all human life," said Mary Ellen Russell, executive director of the Maryland Catholic Conference. "Unfortunately this referendum will only divide the pro-life community and drain scarce time and resources from other more important pro-life goals."

Polling has shown that when Maryland voters are asked whether they favor keeping the death penalty, a narrow majority says yes. However, when asked how they feel about replacing the death penalty with a sentence of life without parole, polls have shown strong support for repeal.

That could make the wording of a ballot question a critical issue. That language is drafted by the secretary of state, an appointee of the governor, but it can be challenged in court.

Shellenberger said any wording that mentions life without parole would likely be litigated.

"That should be challenged because life without parole has been on the books for at least 20 years," he said.

Shellenberger said that without capital punishment, Maryland would not have an appropriate penalty in the case of such incidents as the Boston Marathon bombing and the Newtown, Conn., mass shooting.

Joining Parrott and Shellenberger at the news conference was Sen. Jim Brochin, a Baltimore County Democrat who voted against repeal.

He pointed to a 2009 case in Salisbury in which 11-year-old Sarah Foxwell was abducted from her home, sexually assaulted and murdered. He argued that having the death penalty on the books gave prosecutors the leverage to force the killer to accept a sentence of life without parole.

"Within a week, the defense team knew the death penalty was a possibility, and they took a plea," Brochin said.

michael.dresser@baltsun.com